![Apple M1](https://upload.wikimedia.org/wikipedia/commons/8/83/Apple_M1.jpg)
A system on a chip or system-on-chip (SoC ; pl. ''SoCs'' ) is an
integrated circuit
An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...
that integrates most or all components of a computer or other
electronic system
Electronic may refer to:
*Electronics, the science of how to control electric energy in semiconductor
* ''Electronics'' (magazine), a defunct American trade journal
*Electronic storage, the storage of data using an electronic device
*Electronic co ...
. These components almost always include a
central processing unit
A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, an ...
(CPU),
memory
Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered, ...
interfaces, on-chip
input/output
In computing, input/output (I/O, or informally io or IO) is the communication between an information processing system, such as a computer, and the outside world, possibly a human or another information processing system. Inputs are the signals ...
devices,
input/output
In computing, input/output (I/O, or informally io or IO) is the communication between an information processing system, such as a computer, and the outside world, possibly a human or another information processing system. Inputs are the signals ...
interfaces, and
secondary storage
Computer data storage is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers.
The central processing unit (CPU) of a computer ...
interfaces, often alongside other components such as
radio modem
Radio modems are modems that transfer data wirelessly across a range of up to tens of kilometres.
Using radio modems is a modern way to create Private Radio Networks (PRN). Private radio networks are used in critical industrial applications, when r ...
s and a
graphics processing unit
A graphics processing unit (GPU) is a specialized electronic circuit designed to manipulate and alter memory to accelerate the creation of images in a frame buffer intended for output to a display device. GPUs are used in embedded systems, mobi ...
(GPU) – all on a single
substrate or microchip. It may contain
digital
Digital usually refers to something using discrete digits, often binary digits.
Technology and computing Hardware
*Digital electronics, electronic circuits which operate using digital signals
**Digital camera, which captures and stores digital i ...
,
analog
Analog or analogue may refer to:
Computing and electronics
* Analog signal, in which information is encoded in a continuous variable
** Analog device, an apparatus that operates on analog signals
*** Analog electronics, circuits which use analog ...
,
mixed-signal
A mixed-signal integrated circuit is any integrated circuit that has both analog circuits and digital circuits on a single semiconductor die.[radio frequency
Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the upp ...]
signal processing
Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing ''signals'', such as audio signal processing, sound, image processing, images, and scientific measurements. Signal processing techniq ...
functions (otherwise it is considered only an application processor).
Higher-performance SoCs are often paired with dedicated and physically separate memory and secondary storage (such as
LPDDR
Low-Power Double Data Rate (LPDDR), also known as LPDDR SDRAM, is a type of synchronous dynamic random-access memory that consumes less power and is targeted for mobile computers and devices such as mobile phones. Older variants are also known as ...
and
eUFS
Universal Flash Storage (UFS) is a flash storage specification for digital cameras, mobile phones and consumer electronic devices. It was designed to bring higher data transfer speed and increased reliability to flash memory storage, while reduc ...
or
eMMC
The MultiMediaCard, officially abbreviated as MMC, is a memory card standard used for solid-state storage. Unveiled in 1997 by SanDisk and Siemens, MMC is based on a surface-contact low pin-count serial interface using a single memory stack subs ...
, respectively) chips, that may be layered on top of the SoC in what's known as a
package on package
Package on a package (PoP) is an integrated circuit packaging method to vertically combine discrete logic and memory ball grid array (BGA) packages. Two or more packages are installed atop each other, i.e. stacked, with a standard interface to rout ...
(PoP) configuration, or be placed close to the SoC. Additionally, SoCs may use separate wireless
modem
A modulator-demodulator or modem is a computer hardware device that converts data from a digital format into a format suitable for an analog transmission medium such as telephone or radio. A modem transmits data by Modulation#Digital modulati ...
s.
SoCs are in contrast to the common traditional
motherboard
A motherboard (also called mainboard, main circuit board, mb, mboard, backplane board, base board, system board, logic board (only in Apple computers) or mobo) is the main printed circuit board (PCB) in general-purpose computers and other expand ...
-based
PC architecture
Architecture is the art and technique of designing and building, as distinguished from the skills associated with construction. It is both the process and the product of sketching, conceiving, planning, designing, and constructing building ...
, which separates components based on function and connects them through a central interfacing circuit board.
[This central board is called the "mother board" for hosting the "child" component cards.] Whereas a motherboard houses and connects detachable or replaceable components, SoCs integrate all of these components into a single integrated circuit. An SoC will typically integrate a CPU, graphics and memory interfaces,
[The graphics connections (]PCI Express
PCI Express (Peripheral Component Interconnect Express), officially abbreviated as PCIe or PCI-e, is a high-speed serial computer expansion bus standard, designed to replace the older PCI, PCI-X and AGP bus standards. It is the common ...
) and RAM historically constituted the northbridge of motherboard-backed discrete architectures. secondary storage and USB connectivity,
[The hard disk and USB connectivity historically comprised part of the southbridge of motherboard-backed discrete modular architectures.] random-access
Random access (more precisely and more generally called direct access) is the ability to access an arbitrary element of a sequence in equal time or any datum from a population of addressable elements roughly as easily and efficiently as any othe ...
and
read-only memories
Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered, ...
and secondary storage and/or their controllers on a single circuit die, whereas a motherboard would connect these modules as
discrete components
An electronic component is any basic discrete device or physical entity in an electronic system used to affect electrons or their associated fields. Electronic components are mostly industrial products, available in a singular form and are not ...
or
expansion card
In computing, an expansion card (also called an expansion board, adapter card, peripheral card or accessory card) is a printed circuit board that can be inserted into an electrical connector, or expansion slot (also referred to as a bus slo ...
s.
An SoC integrates a
microcontroller
A microcontroller (MCU for ''microcontroller unit'', often also MC, UC, or μC) is a small computer on a single VLSI integrated circuit (IC) chip. A microcontroller contains one or more CPUs (processor cores) along with memory and programmable i ...
,
microprocessor
A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circu ...
or perhaps several processor cores with peripherals like a
GPU
A graphics processing unit (GPU) is a specialized electronic circuit designed to manipulate and alter memory to accelerate the creation of images in a frame buffer intended for output to a display device. GPUs are used in embedded systems, mobil ...
,
Wi-Fi
Wi-Fi () is a family of wireless network protocols, based on the IEEE 802.11 family of standards, which are commonly used for local area networking of devices and Internet access, allowing nearby digital devices to exchange data by radio wave ...
and
cellular network
A cellular network or mobile network is a communication network where the link to and from end nodes is wireless. The network is distributed over land areas called "cells", each served by at least one fixed-location transceiver (typically thre ...
radio modems, and/or one or more
coprocessor
A coprocessor is a computer processor used to supplement the functions of the primary processor (the CPU). Operations performed by the coprocessor may be floating-point arithmetic, graphics, signal processing, string processing, cryptography o ...
s. Similar to how a microcontroller integrates a microprocessor with peripheral circuits and memory, an SoC can be seen as integrating a microcontroller with even more advanced
peripheral
A peripheral or peripheral device is an auxiliary device used to put information into and get information out of a computer. The term ''peripheral device'' refers to all hardware components that are attached to a computer and are controlled by the ...
s.
Compared to a multi-chip architecture, an SoC with equivalent functionality will have increased
performance
A performance is an act of staging or presenting a play, concert, or other form of entertainment. It is also defined as the action or process of carrying out or accomplishing an action, task, or function.
Management science
In the work place ...
and reduced
power consumption
Electric energy consumption is the form of energy consumption that uses electrical energy. Electric energy consumption is the actual energy demand made on existing electricity supply for transportation, residential, industrial, commercial, and o ...
as well as a smaller
semiconductor die area. This comes at the cost of reduced
replaceability of components. By definition, SoC designs are fully or nearly fully integrated across different component
modules
Broadly speaking, modularity is the degree to which a system's components may be separated and recombined, often with the benefit of flexibility and variety in use. The concept of modularity is used primarily to reduce complexity by breaking a sy ...
. For these reasons, there has been a general trend towards tighter integration of components in the
computer hardware industry, in part due to the influence of SoCs and lessons learned from the mobile and embedded computing markets. SoCs can be viewed as part of a larger trend towards
embedded computing
An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is ''embedded'' as ...
and
hardware acceleration
Hardware acceleration is the use of computer hardware designed to perform specific functions more efficiently when compared to software running on a general-purpose central processing unit (CPU). Any transformation of data that can be calcula ...
.
SoCs are very common in the
mobile computing
Mobile computing is human–computer interaction in which a computer is expected to be transported during normal usage, which allows for the transmission of data, voice, and video. Mobile computing involves mobile communication, mobile hardware ...
(such as in
smartphones
A smartphone is a portable computer device that combines mobile telephone and computing functions into one unit. They are distinguished from feature phones by their stronger hardware capabilities and extensive mobile operating systems, which ...
and
tablet computer
A tablet computer, commonly shortened to tablet, is a mobile device, typically with a mobile operating system and touchscreen display processing circuitry, and a rechargeable battery in a single, thin and flat package. Tablets, being comput ...
s) and
edge computing markets. They are also commonly used in
embedded system
An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is ''embedded'' as ...
s such as WiFi routers and the
Internet of things
The Internet of things (IoT) describes physical objects (or groups of such objects) with sensors, processing ability, software and other technologies that connect and exchange data with other devices and systems over the Internet or other comm ...
.
Types
In general, there are three distinguishable types of SoCs:
* SoCs built around a
microcontroller
A microcontroller (MCU for ''microcontroller unit'', often also MC, UC, or μC) is a small computer on a single VLSI integrated circuit (IC) chip. A microcontroller contains one or more CPUs (processor cores) along with memory and programmable i ...
,
* SoCs built around a
microprocessor
A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circu ...
, often found in mobile phones;
* Specialized
application-specific integrated circuit
An application-specific integrated circuit (ASIC ) is an integrated circuit (IC) chip customized for a particular use, rather than intended for general-purpose use, such as a chip designed to run in a digital voice recorder or a high-efficie ...
SoCs designed for specific applications that do not fit into the above two categories.
Applications
SoCs can be applied to any computing task. However, they are typically used in mobile computing such as tablets, smartphones, smartwatches and netbooks as well as
embedded system
An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is ''embedded'' as ...
s and in applications where previously
microcontroller
A microcontroller (MCU for ''microcontroller unit'', often also MC, UC, or μC) is a small computer on a single VLSI integrated circuit (IC) chip. A microcontroller contains one or more CPUs (processor cores) along with memory and programmable i ...
s would be used.
Embedded systems
Where previously only microcontrollers could be used, SoCs are rising to prominence in the embedded systems market. Tighter system integration offers better reliability and
mean time between failure
Mean time between failures (MTBF) is the predicted elapsed time between inherent failures of a mechanical or electronic system during normal system operation. MTBF can be calculated as the arithmetic mean (average) time between failures of a syste ...
, and SoCs offer more advanced functionality and computing power than microcontrollers. Applications include
AI acceleration, embedded
machine vision
Machine vision (MV) is the technology and methods used to provide imaging-based automatic inspection and analysis for such applications as automatic inspection, process control, and robot guidance, usually in industry. Machine vision refers to m ...
,
data collection
Data collection or data gathering is the process of gathering and measuring information on targeted variables in an established system, which then enables one to answer relevant questions and evaluate outcomes. Data collection is a research com ...
,
telemetry
Telemetry is the in situ data collection, collection of measurements or other data at remote points and their automatic data transmission, transmission to receiving equipment (telecommunication) for monitoring. The word is derived from the Gr ...
,
vector processing
In computing, a vector processor or array processor is a central processing unit (CPU) that implements an instruction set where its instructions are designed to operate efficiently and effectively on large one-dimensional arrays of data called ' ...
and
ambient intelligence
In computing, ambient intelligence (AmI) refers to electronic environments that are sensitive and responsive to the presence of people. Ambient intelligence was a projection on the future of consumer electronics, telecommunications and computing ...
. Often embedded SoCs target the
internet of things
The Internet of things (IoT) describes physical objects (or groups of such objects) with sensors, processing ability, software and other technologies that connect and exchange data with other devices and systems over the Internet or other comm ...
,
industrial internet of things
The industrial internet of things (IIoT) refers to interconnected sensors, instruments, and other devices networked together with computers' industrial applications, including manufacturing and energy management. This connectivity allows for data ...
and
edge computing markets.
Mobile computing
Mobile computing
Mobile computing is human–computer interaction in which a computer is expected to be transported during normal usage, which allows for the transmission of data, voice, and video. Mobile computing involves mobile communication, mobile hardware ...
based SoCs always bundle processors, memories, on-chip
caches,
wireless networking
A wireless network is a computer network that uses wireless data connections between network nodes.
Wireless networking is a method by which homes, telecommunications networks and business installations avoid the costly process of introducing c ...
capabilities and often
digital camera
A digital camera is a camera that captures photographs in digital memory. Most cameras produced today are digital, largely replacing those that capture images on photographic film. Digital cameras are now widely incorporated into mobile device ...
hardware and firmware. With increasing memory sizes, high end SoCs will often have no memory and flash storage and instead, the memory and
flash memory
Flash memory is an electronic non-volatile computer memory storage medium that can be electrically erased and reprogrammed. The two main types of flash memory, NOR flash and NAND flash, are named for the NOR and NAND logic gates. Both us ...
will be placed right next to, or above (
package on package
Package on a package (PoP) is an integrated circuit packaging method to vertically combine discrete logic and memory ball grid array (BGA) packages. Two or more packages are installed atop each other, i.e. stacked, with a standard interface to rout ...
), the SoC. Some examples of mobile computing SoCs include:
*
Samsung Electronics
Samsung Electronics Co., Ltd. (, sometimes shortened to SEC and stylized as SΛMSUNG) is a South Korean multinational corporation, multinational electronics corporation headquartered in Yeongtong-gu, Suwon, South Korea. It is the pinnacle of ...
:
list
A ''list'' is any set of items in a row. List or lists may also refer to:
People
* List (surname)
Organizations
* List College, an undergraduate division of the Jewish Theological Seminary of America
* SC Germania List, German rugby union ...
, typically based on
ARM
In human anatomy, the arm refers to the upper limb in common usage, although academically the term specifically means the upper arm between the glenohumeral joint (shoulder joint) and the elbow joint. The distal part of the upper limb between the ...
**
Exynos
Exynos, formerly Hummingbird (), is a series of ARM-based system-on-chips developed by Samsung Electronics' System LSI division and manufactured by Samsung Foundry. It is a continuation of Samsung's earlier S3C, S5L and S5P line of SoCs.
Exy ...
, used mainly by Samsung's
Galaxy
A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. ...
series of smartphones
*
Qualcomm
Qualcomm () is an American multinational corporation headquartered in San Diego, California, and incorporated in Delaware. It creates semiconductors, software, and services related to wireless technology. It owns patents critical to the 5G, 4 ...
:
**
Snapdragon
''Antirrhinum'' is a genus of plants commonly known as dragon flowers, snapdragons and dog flower because of the flowers' fancied resemblance to the face of a dragon that opens and closes its mouth when laterally squeezed. They are native to r ...
(
list
A ''list'' is any set of items in a row. List or lists may also refer to:
People
* List (surname)
Organizations
* List College, an undergraduate division of the Jewish Theological Seminary of America
* SC Germania List, German rugby union ...
), used in many
LG,
Xiaomi
Corporation (; ), commonly known as Xiaomi and registered as Xiaomi Inc., is a Chinese designer and manufacturer of consumer electronics and related software, home appliances, and household items. Behind Samsung, it is the second largest ma ...
,
Google Pixel
Google Pixel is a brand of consumer electronic devices developed by Google that run either ChromeOS or the Android operating system. The Pixel brand was introduced in February 2013 with the first-generation Chromebook Pixel. The Pixel line inclu ...
,
HTC
HTC Corporation ( zh, t=宏達國際電子股份有限公司, s=宏达国际电子股份有限公司, p=Hóngdá Guójì Diànzǐ Gǔfèn Yǒuxiàn Gōngsī, first=t) or High Tech Computer Corporation, (literally ''Hongda International Electron ...
and Samsung Galaxy smartphones. In 2018, Snapdragon SoCs are being used as the backbone of
laptop computers
A laptop, laptop computer, or notebook computer is a small, portable personal computer (PC) with a screen and alphanumeric keyboard. Laptops typically have a clam shell form factor with the screen mounted on the inside of the upper li ...
running
Windows 10
Windows 10 is a major release of Microsoft's Windows NT operating system. It is the direct successor to Windows 8.1, which was released nearly two years earlier. It was released to manufacturing on July 15, 2015, and later to retail on J ...
, marketed as "Always Connected PCs".
Personal computers
In 1992,
Acorn Computers
Acorn Computers Ltd. was a British computer company established in Cambridge, England, in 1978. The company produced a number of computers which were especially popular in the United Kingdom, UK, including the Acorn Electron and the Acorn Archi ...
produced the
A3010, A3020 and A4000 range of personal computers with the ARM250 SoC. It combined the original Acorn ARM2 processor with a memory controller (MEMC), video controller (VIDC), and I/O controller (IOC). In previous Acorn
ARM
In human anatomy, the arm refers to the upper limb in common usage, although academically the term specifically means the upper arm between the glenohumeral joint (shoulder joint) and the elbow joint. The distal part of the upper limb between the ...
-powered computers, these were four discrete chips. The ARM7500 chip was their second-generation SoC, based on the ARM700, VIDC20 and IOMD controllers, and was widely licensed in embedded devices such as set-top-boxes, as well as later Acorn personal computers.
SoCs are being applied to mainstream personal computers as of 2018.
They are particularly applied to laptops and
tablet PCs. Tablet and laptop manufacturers have learned lessons from embedded systems and smartphone markets about reduced power consumption, better performance and reliability from tighter
integration
Integration may refer to:
Biology
*Multisensory integration
*Path integration
* Pre-integration complex, viral genetic material used to insert a viral genome into a host genome
*DNA integration, by means of site-specific recombinase technology, ...
of hardware and
firmware
In computing, firmware is a specific class of computer software that provides the low-level control for a device's specific hardware. Firmware, such as the BIOS of a personal computer, may contain basic functions of a device, and may provide h ...
modules
Broadly speaking, modularity is the degree to which a system's components may be separated and recombined, often with the benefit of flexibility and variety in use. The concept of modularity is used primarily to reduce complexity by breaking a sy ...
, and
LTE and other
wireless network
A wireless network is a computer network that uses wireless data connections between network nodes.
Wireless networking is a method by which homes, telecommunications networks and business installations avoid the costly process of introducing c ...
communications integrated on chip (integrated
network interface controller
A network interface controller (NIC, also known as a network interface card, network adapter, LAN adapter or physical network interface, and by similar terms) is a computer hardware component that connects a computer to a computer network.
Ear ...
s).
ARM
In human anatomy, the arm refers to the upper limb in common usage, although academically the term specifically means the upper arm between the glenohumeral joint (shoulder joint) and the elbow joint. The distal part of the upper limb between the ...
-based:
*
Qualcomm Snapdragon
Snapdragon is a suite of system on a chip (SoC) semiconductor products for mobile devices designed and marketed by Qualcomm Technologies Inc. The Snapdragon's central processing unit (CPU) uses the ARM architecture. A single SoC may include mu ...
*
Apple M1
Apple M1 is a series of ARM architecture, ARM-based system-on-a-chip, systems-on-a-chip (SoCs) Apple silicon, designed by Apple Inc. as a central processing unit (CPU) and graphics processing unit (GPU) for its Mac (computer), Mac desktop compu ...
x86
x86 (also known as 80x86 or the 8086 family) is a family of complex instruction set computer (CISC) instruction set architectures initially developed by Intel based on the Intel 8086 microprocessor and its 8088 variant. The 8086 was introd ...
-based:
*
Intel Core
Intel Core is a line of streamlined midrange consumer, workstation and enthusiast computer central processing units (CPUs) marketed by Intel Corporation. These processors displaced the existing mid- to high-end Pentium processors at the time ...
CULV
Consumer Ultra-Low Voltage (CULV) is a computing platform developed by Intel.[functional unit
In computer engineering, an execution unit (E-unit or EU) is a part of the central processing unit (CPU) that performs the operations and calculations as instructed by the computer program. It may have its own internal control sequence unit (not ...](_blank)
s, including
microprocessor
A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circu ...
s that run
software code
A computer program is a sequence or set of instructions in a programming language for a computer to execute. Computer programs are one component of software, which also includes documentation and other intangible components.
A computer program ...
, as well as a
communications subsystem
A communications system or communication system is a collection of individual telecommunications networks, transmission systems, relay stations, tributary stations, and terminal equipment usually capable of interconnection and interoperat ...
to connect, control, direct and interface between these functional modules.
Functional components
Processor cores
An SoC must have at least one
processor core
A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, and ...
, but typically an SoC has more than one core. Processor cores can be a
microcontroller
A microcontroller (MCU for ''microcontroller unit'', often also MC, UC, or μC) is a small computer on a single VLSI integrated circuit (IC) chip. A microcontroller contains one or more CPUs (processor cores) along with memory and programmable i ...
,
microprocessor
A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circu ...
(μP),
digital signal processor
A digital signal processor (DSP) is a specialized microprocessor chip, with its architecture optimized for the operational needs of digital signal processing. DSPs are fabricated on MOS integrated circuit chips. They are widely used in audio si ...
(DSP) or
application-specific instruction set processor
An application-specific instruction set processor (ASIP) is a component used in system on a chip design. The instruction set architecture of an ASIP is tailored to benefit a specific application. This specialization of the core provides a tradeo ...
(ASIP) core.
ASIPs have
instruction sets
In computer science, an instruction set architecture (ISA), also called computer architecture, is an abstract model of a computer. A device that executes instructions described by that ISA, such as a central processing unit (CPU), is called an ' ...
that are customized for an
application domain
An application domain is a mechanism (similar to a process in an operating system) used within the Common Language Infrastructure (CLI) to isolate executed software applications from one another so that they do not affect each other. Each applicati ...
and designed to be more efficient than general-purpose instructions for a specific type of workload.
Multiprocessor SoCs have more than one processor core by definition.
Whether single-core,
multi-core
A multi-core processor is a microprocessor on a single integrated circuit with two or more separate processing units, called cores, each of which reads and executes program instructions. The instructions are ordinary CPU instructions (such a ...
or
manycore
Manycore processors are special kinds of multi-core processors designed for a high degree of parallel processing, containing numerous simpler, independent processor cores (from a few tens of cores to thousands or more). Manycore processors are use ...
, SoC processor cores typically use
RISC
In computer engineering, a reduced instruction set computer (RISC) is a computer designed to simplify the individual instructions given to the computer to accomplish tasks. Compared to the instructions given to a complex instruction set comput ...
instruction set architectures. RISC architectures are advantageous over
CISC processors for SoCs because they require less digital logic, and therefore less power and area on
board
Board or Boards may refer to:
Flat surface
* Lumber, or other rigid material, milled or sawn flat
** Plank (wood)
** Cutting board
** Sounding board, of a musical instrument
* Cardboard (paper product)
* Paperboard
* Fiberboard
** Hardboard, a ty ...
, and in the
embedded and
mobile computing
Mobile computing is human–computer interaction in which a computer is expected to be transported during normal usage, which allows for the transmission of data, voice, and video. Mobile computing involves mobile communication, mobile hardware ...
markets, area and power are often highly constrained. In particular, SoC processor cores often use the
ARM architecture
ARM (stylised in lowercase as arm, formerly an acronym for Advanced RISC Machines and originally Acorn RISC Machine) is a family of reduced instruction set computer (RISC) instruction set architectures for computer processors, configured ...
because it is a
soft processor specified as an
IP core
In electronic design, a semiconductor intellectual property core (SIP core), IP core, or IP block is a reusable unit of logic, cell, or integrated circuit layout design that is the intellectual property of one party. IP cores can be licensed to ...
and is more power efficient than
x86
x86 (also known as 80x86 or the 8086 family) is a family of complex instruction set computer (CISC) instruction set architectures initially developed by Intel based on the Intel 8086 microprocessor and its 8088 variant. The 8086 was introd ...
.
Memory
SoCs must have
semiconductor memory
Semiconductor memory is a digital electronic semiconductor device used for digital data storage, such as computer memory. It typically refers to devices in which data is stored within metal–oxide–semiconductor (MOS) memory cells on a sili ...
blocks to perform their computation, as do
microcontroller
A microcontroller (MCU for ''microcontroller unit'', often also MC, UC, or μC) is a small computer on a single VLSI integrated circuit (IC) chip. A microcontroller contains one or more CPUs (processor cores) along with memory and programmable i ...
s and other
embedded system
An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is ''embedded'' as ...
s. Depending on the application, SoC memory may form a
memory hierarchy
In computer architecture, the memory hierarchy separates computer storage into a hierarchy based on response time. Since response time, complexity, and capacity are related, the levels may also be distinguished by their performance and controlli ...
and
cache hierarchy
Cache hierarchy, or multi-level caches, refers to a memory architecture that uses a hierarchy of memory stores based on varying access speeds to cache data. Highly requested data is cached in high-speed access memory stores, allowing swifter access ...
. In the mobile computing market, this is common, but in many
low-power embedded microcontrollers, this is not necessary. Memory technologies for SoCs include
read-only memory
Read-only memory (ROM) is a type of non-volatile memory used in computers and other electronic devices. Data stored in ROM cannot be electronically modified after the manufacture of the memory device. Read-only memory is useful for storing sof ...
(ROM),
random-access memory
Random-access memory (RAM; ) is a form of computer memory that can be read and changed in any order, typically used to store working Data (computing), data and machine code. A Random access, random-access memory device allows data items to b ...
(RAM), Electrically Erasable Programmable ROM (
EEPROM
EEPROM (also called E2PROM) stands for electrically erasable programmable read-only memory and is a type of non-volatile memory used in computers, usually integrated in microcontrollers such as smart cards and remote keyless systems, or as a ...
) and
flash memory
Flash memory is an electronic non-volatile computer memory storage medium that can be electrically erased and reprogrammed. The two main types of flash memory, NOR flash and NAND flash, are named for the NOR and NAND logic gates. Both us ...
.
As in other computer systems, RAM can be subdivided into relatively faster but more expensive
static RAM
Static random-access memory (static RAM or SRAM) is a type of random-access memory (RAM) that uses latching circuitry (flip-flop) to store each bit. SRAM is volatile memory; data is lost when power is removed.
The term ''static'' differen ...
(SRAM) and the slower but cheaper
dynamic RAM
Dynamic random-access memory (dynamic RAM or DRAM) is a type of random-access semiconductor memory that stores each bit of data in a memory cell, usually consisting of a tiny capacitor and a transistor, both typically based on metal-oxide ...
(DRAM). When an SoC has a
cache
Cache, caching, or caché may refer to:
Places United States
* Cache, Idaho, an unincorporated community
* Cache, Illinois, an unincorporated community
* Cache, Oklahoma, a city in Comanche County
* Cache, Utah, Cache County, Utah
* Cache Count ...
hierarchy, SRAM will usually be used to implement
processor register
A processor register is a quickly accessible location available to a computer's processor. Registers usually consist of a small amount of fast storage, although some registers have specific hardware functions, and may be read-only or write-only. ...
s and cores'
built-in caches whereas DRAM will be used for
main memory
Computer data storage is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers.
The central processing unit (CPU) of a computer ...
. "Main memory" may be specific to a single processor (which can be
multi-core
A multi-core processor is a microprocessor on a single integrated circuit with two or more separate processing units, called cores, each of which reads and executes program instructions. The instructions are ordinary CPU instructions (such a ...
) when the SoC
has multiple processors, in this case it is
distributed memory
In computer science, distributed memory refers to a multiprocessor computer system in which each processor has its own private memory. Computational tasks can only operate on local data, and if remote data are required, the computational task mu ...
and must be sent via on-chip to be accessed by a different processor.
For further discussion of multi-processing memory issues, see
cache coherence
In computer architecture, cache coherence is the uniformity of shared resource data that ends up stored in multiple local caches. When clients in a system maintain caches of a common memory resource, problems may arise with incoherent data, whi ...
and
memory latency
''Memory latency'' is the time (the latency) between initiating a request for a byte or word in memory until it is retrieved by a processor. If the data are not in the processor's cache, it takes longer to obtain them, as the processor will hav ...
.
Interfaces
SoCs include external
interfaces
Interface or interfacing may refer to:
Academic journals
* Interface (journal), ''Interface'' (journal), by the Electrochemical Society
* ''Interface, Journal of Applied Linguistics'', now merged with ''ITL International Journal of Applied Lin ...
, typically for
communication protocol
A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics (computer scien ...
s. These are often based upon industry standards such as
USB
Universal Serial Bus (USB) is an industry standard that establishes specifications for cables, connectors and protocols for connection, communication and power supply (interfacing) between computers, peripherals and other computers. A broad v ...
,
FireWire
IEEE 1394 is an interface standard for a serial bus for high-speed communications and isochronous real-time data transfer. It was developed in the late 1980s and early 1990s by Apple in cooperation with a number of companies, primarily Sony an ...
,
Ethernet
Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 198 ...
,
USART A universal synchronous and asynchronous receiver-transmitter (USART, programmable communications interface or PCI) is a type of a serial interface device that can be programmed to communicate asynchronously or synchronously. See universal asynchron ...
,
SPI,
HDMI
High-Definition Multimedia Interface (HDMI) is a proprietary audio/video interface for transmitting uncompressed video data and compressed or uncompressed digital audio data from an HDMI-compliant source device, such as a display controller, ...
,
I²C
I2C (Inter-Integrated Circuit, ), alternatively known as I2C or IIC, is a synchronous, multi-controller/multi-target (master/slave), packet switched, single-ended, serial communication bus invented in 1982 by Philips Semiconductors. It is wide ...
, etc. These interfaces will differ according to the intended application.
Wireless network
A wireless network is a computer network that uses wireless data connections between network nodes.
Wireless networking is a method by which homes, telecommunications networks and business installations avoid the costly process of introducing c ...
ing protocols such as
Wi-Fi
Wi-Fi () is a family of wireless network protocols, based on the IEEE 802.11 family of standards, which are commonly used for local area networking of devices and Internet access, allowing nearby digital devices to exchange data by radio wave ...
,
Bluetooth
Bluetooth is a short-range wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances and building personal area networks (PANs). In the most widely used mode, transmission power is limi ...
,
6LoWPAN
6LoWPAN (acronym of "IPv6 over Low-Power Wireless Personal Area Networks") in '6LoWPAN: The Embedded Internet', Shelby and Bormann redefine the 6LoWPAN acronym as "IPv6 over lowpower wireless area networks," arguing that "Personal" is no longer rel ...
and
near-field communication
Near-field communication (NFC) is a set of communication protocols that enables communication between two electronic devices over a distance of 4 cm (1 in) or less. NFC offers a low-speed connection through a simple setup that can be u ...
may also be supported.
When needed, SoCs include
analog
Analog or analogue may refer to:
Computing and electronics
* Analog signal, in which information is encoded in a continuous variable
** Analog device, an apparatus that operates on analog signals
*** Analog electronics, circuits which use analog ...
interfaces including
analog-to-digital
In electronics, an analog-to-digital converter (ADC, A/D, or A-to-D) is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a digital signal. An ADC may also provide ...
and
digital-to-analog converter
In electronics, a digital-to-analog converter (DAC, D/A, D2A, or D-to-A) is a system that converts a digital signal into an analog signal. An analog-to-digital converter (ADC) performs the reverse function.
There are several DAC architec ...
s, often for
signal processing
Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing ''signals'', such as audio signal processing, sound, image processing, images, and scientific measurements. Signal processing techniq ...
. These may be able to interface with different types of
sensor
A sensor is a device that produces an output signal for the purpose of sensing a physical phenomenon.
In the broadest definition, a sensor is a device, module, machine, or subsystem that detects events or changes in its environment and sends ...
s or
actuator
An actuator is a component of a machine that is responsible for moving and controlling a mechanism or system, for example by opening a valve. In simple terms, it is a "mover".
An actuator requires a control device (controlled by control signal) a ...
s, including
smart transducer
A smart transducer is an analog or digital transducer, actuator or sensor combined with a processing unit and a communication interface.
As sensors and actuators become more complex they provide support for various modes of operation and interf ...
s. They may interface with application-specific
modules
Broadly speaking, modularity is the degree to which a system's components may be separated and recombined, often with the benefit of flexibility and variety in use. The concept of modularity is used primarily to reduce complexity by breaking a sy ...
or shields.
[In ]embedded system
An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is ''embedded'' as ...
s, "shields" are analogous to expansion card
In computing, an expansion card (also called an expansion board, adapter card, peripheral card or accessory card) is a printed circuit board that can be inserted into an electrical connector, or expansion slot (also referred to as a bus slo ...
s for PCs
A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or techn ...
. They often fit over a microcontroller
A microcontroller (MCU for ''microcontroller unit'', often also MC, UC, or μC) is a small computer on a single VLSI integrated circuit (IC) chip. A microcontroller contains one or more CPUs (processor cores) along with memory and programmable i ...
such as an Arduino
Arduino () is an open-source hardware and software company, project, and user community that designs and manufactures single-board microcontrollers and microcontroller kits for building digital devices. Its hardware products are licensed unde ...
or single-board computer
A single-board computer (SBC) is a complete computer built on a single circuit board, with microprocessor(s), memory, input/output (I/O) and other features required of a functional computer. Single-board computers are commonly made as demonstrati ...
such as the Raspberry Pi
Raspberry Pi () is a series of small single-board computers (SBCs) developed in the United Kingdom by the Raspberry Pi Foundation in association with Broadcom. The Raspberry Pi project originally leaned towards the promotion of teaching basic ...
and function as peripheral
A peripheral or peripheral device is an auxiliary device used to put information into and get information out of a computer. The term ''peripheral device'' refers to all hardware components that are attached to a computer and are controlled by the ...
s for the device. Or they may be internal to the SoC, such as if an analog sensor is built in to the SoC and its readings must be converted to digital signals for mathematical processing.
Digital signal processors
Digital signal processor
A digital signal processor (DSP) is a specialized microprocessor chip, with its architecture optimized for the operational needs of digital signal processing. DSPs are fabricated on MOS integrated circuit chips. They are widely used in audio si ...
(DSP) cores are often included on SoCs. They perform
signal processing
Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing ''signals'', such as audio signal processing, sound, image processing, images, and scientific measurements. Signal processing techniq ...
operations in SoCs for
sensor
A sensor is a device that produces an output signal for the purpose of sensing a physical phenomenon.
In the broadest definition, a sensor is a device, module, machine, or subsystem that detects events or changes in its environment and sends ...
s,
actuator
An actuator is a component of a machine that is responsible for moving and controlling a mechanism or system, for example by opening a valve. In simple terms, it is a "mover".
An actuator requires a control device (controlled by control signal) a ...
s,
data collection
Data collection or data gathering is the process of gathering and measuring information on targeted variables in an established system, which then enables one to answer relevant questions and evaluate outcomes. Data collection is a research com ...
,
data analysis
Data analysis is a process of inspecting, cleansing, transforming, and modeling data with the goal of discovering useful information, informing conclusions, and supporting decision-making. Data analysis has multiple facets and approaches, enco ...
and multimedia processing. DSP cores typically feature
very long instruction word
Very long instruction word (VLIW) refers to instruction set architectures designed to exploit instruction level parallelism (ILP). Whereas conventional central processing units (CPU, processor) mostly allow programs to specify instructions to exe ...
(VLIW) and
single instruction, multiple data
Single instruction, multiple data (SIMD) is a type of parallel processing in Flynn's taxonomy. SIMD can be internal (part of the hardware design) and it can be directly accessible through an instruction set architecture (ISA), but it should ...
(SIMD)
instruction set architecture
In computer science, an instruction set architecture (ISA), also called computer architecture, is an abstract model of a computer. A device that executes instructions described by that ISA, such as a central processing unit (CPU), is called an ' ...
s, and are therefore highly amenable to exploiting
instruction-level parallelism
Instruction-level parallelism (ILP) is the parallel or simultaneous execution of a sequence of instructions in a computer program. More specifically ILP refers to the average number of instructions run per step of this parallel execution.
Discu ...
through
parallel processing and
superscalar execution.
DSP cores most often feature application-specific instructions, and as such are typically
application-specific instruction set processor
An application-specific instruction set processor (ASIP) is a component used in system on a chip design. The instruction set architecture of an ASIP is tailored to benefit a specific application. This specialization of the core provides a tradeo ...
s (ASIP). Such application-specific instructions correspond to dedicated hardware
functional unit
In computer engineering, an execution unit (E-unit or EU) is a part of the central processing unit (CPU) that performs the operations and calculations as instructed by the computer program. It may have its own internal control sequence unit (not ...
s that compute those instructions.
Typical DSP instructions include
multiply-accumulate,
Fast Fourier transform
A fast Fourier transform (FFT) is an algorithm that computes the discrete Fourier transform (DFT) of a sequence, or its inverse (IDFT). Fourier analysis converts a signal from its original domain (often time or space) to a representation in th ...
,
fused multiply-add
Fuse or FUSE may refer to:
Devices
* Fuse (electrical), a device used in electrical systems to protect against excessive current
** Fuse (automotive), a class of fuses for vehicles
* Fuse (hydraulic), a device used in hydraulic systems to protect ...
, and
convolution
In mathematics (in particular, functional analysis), convolution is a operation (mathematics), mathematical operation on two function (mathematics), functions ( and ) that produces a third function (f*g) that expresses how the shape of one is ...
s.
Other
As with other computer systems, SoCs require
timing sources to generate
clock signal
In electronics and especially synchronous digital circuits, a clock signal (historically also known as ''logic beat'') oscillates between a high and a low state and is used like a metronome to coordinate actions of digital circuits.
A clock sign ...
s, control execution of SoC functions and provide time context to
signal processing
Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing ''signals'', such as audio signal processing, sound, image processing, images, and scientific measurements. Signal processing techniq ...
applications of the SoC, if needed. Popular time sources are
crystal oscillators
A crystal oscillator is an electronic oscillator circuit that uses a piezoelectric crystal as a frequency-selective element. The oscillator frequency is often used to keep track of time, as in quartz wristwatches, to provide a stable clock ...
and
phase-locked loop
A phase-locked loop or phase lock loop (PLL) is a control system that generates an output signal whose phase is related to the phase of an input signal. There are several different types; the simplest is an electronic circuit consisting of a ...
s.
SoC
peripheral
A peripheral or peripheral device is an auxiliary device used to put information into and get information out of a computer. The term ''peripheral device'' refers to all hardware components that are attached to a computer and are controlled by the ...
s including
counter
Counter may refer to:
Mathematics and computing
* Counter machine, a subclass of register machines
* Counter (digital), an electronic device, mechanical device, or computer program for counting
* Loop counter, the variable that controls the iter ...
-timers, real-time
timer
A timer is a specialized type of clock used for measuring specific time intervals.
Timers can be categorized into two main types.
The word "timer" is usually reserved for devices that counts down from a specified time interval, while devices th ...
s and
power-on reset
A power-on reset (PoR, POR) generator is a microcontroller or microprocessor peripheral that generates a reset signal when power is applied to the device. It ensures that the device starts operating in a known state.
PoR generator
In VLSI dev ...
generators. SoCs also include
voltage regulator
A voltage regulator is a system designed to automatically maintain a constant voltage. A voltage regulator may use a simple feed-forward design or may include negative feedback. It may use an electromechanical mechanism, or electronic components ...
s and
power management
Power management is a feature of some electrical appliances, especially copiers, computers, computer CPUs, computer GPUs and computer peripherals such as monitors and printers, that turns off the power or switches the system to a low-power stat ...
circuits.
Intermodule communication
SoCs comprise many
execution unit
In computer engineering, an execution unit (E-unit or EU) is a part of the central processing unit (CPU) that performs the operations and calculations as instructed by the computer program. It may have its own internal control sequence unit (not ...
s. These units must often send data and
instructions
Instruction or instructions may refer to:
Computing
* Instruction, one operation of a processor within a computer architecture instruction set
* Computer program, a collection of instructions
Music
* Instruction (band), a 2002 rock band from Ne ...
back and forth. Because of this, all but the most trivial SoCs require
communications subsystems. Originally, as with other
microcomputer
A microcomputer is a small, relatively inexpensive computer having a central processing unit (CPU) made out of a microprocessor. The computer also includes memory and input/output (I/O) circuitry together mounted on a printed circuit board (PC ...
technologies,
data bus
In computer architecture, a bus (shortened form of the Latin '' omnibus'', and historically also called data highway or databus) is a communication system that transfers data between components inside a computer, or between computers. This ex ...
architectures were used, but recently designs based on sparse intercommunication networks known as
networks-on-chip (NoC) have risen to prominence and are forecast to overtake bus architectures for SoC design in the near future.
Bus-based communication
Historically, a shared global
computer bus
In computer architecture, a bus (shortened form of the Latin '' omnibus'', and historically also called data highway or databus) is a communication system that transfers data between components inside a computer, or between computers. This ex ...
typically connected the different components, also called "blocks" of the SoC.
A very common bus for SoC communications is ARM's royalty-free Advanced Microcontroller Bus Architecture (
AMBA
Amba or AMBA may refer to:
Title
* Amba Hor, alternative name for Abhor and Mehraela, Christian martyrs
* Amba Sada, also known as Psote, Christian bishop and martyr in Upper Egypt
Given name
* Amba, the traditional first name given to the first ...
) standard.
Direct memory access
Direct memory access (DMA) is a feature of computer systems and allows certain hardware subsystems to access main system memory independently of the central processing unit (CPU).
Without DMA, when the CPU is using programmed input/output, it is t ...
controllers route data directly between external interfaces and SoC memory, bypassing the CPU or
control unit
The control unit (CU) is a component of a computer's central processing unit (CPU) that directs the operation of the processor. A CU typically uses a binary decoder to convert coded instructions into timing and control signals that direct the ope ...
, thereby increasing the data
throughput
Network throughput (or just throughput, when in context) refers to the rate of message delivery over a communication channel, such as Ethernet or packet radio, in a communication network. The data that these messages contain may be delivered ov ...
of the SoC. This is similar to some
device driver
In computing, a device driver is a computer program that operates or controls a particular type of device that is attached to a computer or automaton. A driver provides a software interface to hardware devices, enabling operating systems and ot ...
s of peripherals on component-based
multi-chip module
A multi-chip module (MCM) is generically an electronic assembly (such as a package with a number of conductor terminals or "pins") where multiple integrated circuits (ICs or "chips"), semiconductor dies and/or other discrete components are int ...
PC architectures.
Computer buses are limited in
scalability
Scalability is the property of a system to handle a growing amount of work by adding resources to the system.
In an economic context, a scalable business model implies that a company can increase sales given increased resources. For example, a ...
, supporting only up to tens of cores (
multicore
A multi-core processor is a microprocessor on a single integrated circuit with two or more separate processing units, called cores, each of which reads and executes program instructions. The instructions are ordinary CPU instructions (such a ...
) on a single chip.
Wire delay is not scalable due to continued
miniaturization
Miniaturization ( Br.Eng.: ''Miniaturisation'') is the trend to manufacture ever smaller mechanical, optical and electronic products and devices. Examples include miniaturization of mobile phones, computers and vehicle engine downsizing. In ele ...
,
system performance does not scale with the number of cores attached, the SoC's
operating frequency
In computing, the clock rate or clock speed typically refers to the frequency at which the clock generator of a Microprocessor, processor can generate Clock signal, pulses, which are used to Synchronization (computer science), synchronize the op ...
must decrease with each additional core attached for power to be sustainable, and long wires consume large amounts of electrical power. These challenges are prohibitive to supporting
manycore
Manycore processors are special kinds of multi-core processors designed for a high degree of parallel processing, containing numerous simpler, independent processor cores (from a few tens of cores to thousands or more). Manycore processors are use ...
systems on chip.
Network on a chip
In the late 2010s, a trend of SoCs implementing
communications subsystem
A communications system or communication system is a collection of individual telecommunications networks, transmission systems, relay stations, tributary stations, and terminal equipment usually capable of interconnection and interoperat ...
s in terms of a network-like topology instead of
bus-based protocols has emerged. A trend towards
more processor cores on SoCs has caused on-chip communication efficiency to become one of the key factors in determining the overall system performance and cost.
This has led to the emergence of interconnection networks with
router-based
packet switching
In telecommunications, packet switching is a method of grouping Data (computing), data into ''network packet, packets'' that are transmitted over a digital Telecommunications network, network. Packets are made of a header (computing), header and ...
known as "
networks on chip" (NoCs) to overcome the
bottlenecks of bus-based networks.
Networks-on-chip have advantages including destination- and application-specific
routing
Routing is the process of selecting a path for traffic in a network or between or across multiple networks. Broadly, routing is performed in many types of networks, including circuit-switched networks, such as the public switched telephone netw ...
, greater power efficiency and reduced possibility of
bus contention
Bus contention is an undesirable state in computer design where more than one device on a bus attempts to place values on it at the same time.
Bus contention is the kind of telecommunication contention that occurs when all communicating devi ...
. Network-on-chip architectures take inspiration from
communication protocols
A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synchron ...
like
TCP
TCP may refer to:
Science and technology
* Transformer coupled plasma
* Tool Center Point, see Robot end effector
Computing
* Transmission Control Protocol, a fundamental Internet standard
* Telephony control protocol, a Bluetooth communication s ...
and the
Internet protocol suite
The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the set of communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suit ...
for on-chip communication,
although they typically have fewer
network layer
In the seven-layer OSI model of computer networking, the network layer is layer 3. The network layer is responsible for packet forwarding including routing through intermediate routers.
Functions
The network layer provides the means of transfe ...
s. Optimal network-on-chip
network architecture
Network architecture is the design of a computer network. It is a framework for the specification of a network's physical components and their functional organization and configuration, its operational principles and procedures, as well as commun ...
s are an ongoing area of much research interest. NoC architectures range from traditional distributed computing
network topologies
Network topology is the arrangement of the elements ( links, nodes, etc.) of a communication network. Network topology can be used to define or describe the arrangement of various types of telecommunication networks, including command and contro ...
such as
torus
In geometry, a torus (plural tori, colloquially donut or doughnut) is a surface of revolution generated by revolving a circle in three-dimensional space about an axis that is coplanar with the circle.
If the axis of revolution does not tou ...
,
hypercube
In geometry, a hypercube is an ''n''-dimensional analogue of a square () and a cube (). It is a closed, compact, convex figure whose 1- skeleton consists of groups of opposite parallel line segments aligned in each of the space's dimensions, ...
,
meshes
A mesh is a barrier made of connected strands of metal, fiber, or other flexible or ductile materials. A mesh is similar to a web or a net in that it has many attached or woven strands.
Types
* A plastic mesh may be extruded, oriented, ex ...
and
tree network
A tree topology, or star-bus topology, is a hybrid network topology in which star networks are interconnected via bus networks. Tree networks are hierarchical, and each node
In general, a node is a localized swelling (a "knot") or a point of in ...
s to
genetic algorithm scheduling
The genetic algorithm is an operational research method that may be used to solve scheduling problems in production planning.
Importance of production scheduling
To be competitive, corporations must minimize inefficiencies and maximize productivit ...
to
randomized algorithm
A randomized algorithm is an algorithm that employs a degree of randomness as part of its logic or procedure. The algorithm typically uses uniformly random bits as an auxiliary input to guide its behavior, in the hope of achieving good performan ...
s such as
random walks with branching and randomized
time to live
Time to live (TTL) or hop limit is a mechanism which limits the lifespan or lifetime of data in a computer or network. TTL may be implemented as a counter or timestamp attached to or embedded in the data. Once the prescribed event count or timesp ...
(TTL).
Many SoC researchers consider NoC architectures to be the future of SoC design because they have been shown to efficiently meet power and throughput needs of SoC designs. Current NoC architectures are two-dimensional. 2D IC design has limited
floorplanning choices as the number of cores in SoCs increase, so as
three-dimensional integrated circuit
A three-dimensional integrated circuit (3D IC) is a MOSFET, MOS (metal-oxide semiconductor) integrated circuit (IC) manufactured by stacking as many as 16 or more ICs and interconnecting them vertically using, for instance, through-silicon vias (TS ...
s (3DICs) emerge, SoC designers are looking towards building three-dimensional on-chip networks known as 3DNoCs.
Design flow
A system on a chip consists of both the
hardware, described in , and the software controlling the microcontroller, microprocessor or digital signal processor cores, peripherals and interfaces. The
design flow for an SoC aims to develop this hardware and software at the same time, also known as architectural co-design. The design flow must also take into account optimizations () and constraints.
Most SoCs are developed from pre-qualified hardware component
IP core specifications for the hardware elements and
execution unit
In computer engineering, an execution unit (E-unit or EU) is a part of the central processing unit (CPU) that performs the operations and calculations as instructed by the computer program. It may have its own internal control sequence unit (not ...
s, collectively "blocks", described above, together with software
device driver
In computing, a device driver is a computer program that operates or controls a particular type of device that is attached to a computer or automaton. A driver provides a software interface to hardware devices, enabling operating systems and ot ...
s that may control their operation. Of particular importance are the
protocol stack
The protocol stack or network stack is an implementation of a computer networking protocol suite or protocol family. Some of these terms are used interchangeably but strictly speaking, the ''suite'' is the definition of the communication protoco ...
s that drive industry-standard interfaces like
USB
Universal Serial Bus (USB) is an industry standard that establishes specifications for cables, connectors and protocols for connection, communication and power supply (interfacing) between computers, peripherals and other computers. A broad v ...
. The hardware blocks are put together using
computer-aided design
Computer-aided design (CAD) is the use of computers (or ) to aid in the creation, modification, analysis, or optimization of a design. This software is used to increase the productivity of the designer, improve the quality of design, improve c ...
tools, specifically
electronic design automation
Electronic design automation (EDA), also referred to as electronic computer-aided design (ECAD), is a category of software tools for designing Electronics, electronic systems such as integrated circuits and printed circuit boards. The tools wo ...
tools; the
software modules are integrated using a software
integrated development environment
An integrated development environment (IDE) is a software application that provides comprehensive facilities to computer programmers for software development. An IDE normally consists of at least a source code editor, build automation tools a ...
.
SoCs components are also often designed in
high-level programming language
In computer science, a high-level programming language is a programming language with strong Abstraction (computer science), abstraction from the details of the computer. In contrast to low-level programming languages, it may use natural language ...
s such as
C++
C++ (pronounced "C plus plus") is a high-level general-purpose programming language created by Danish computer scientist Bjarne Stroustrup as an extension of the C programming language, or "C with Classes". The language has expanded significan ...
,
MATLAB
MATLAB (an abbreviation of "MATrix LABoratory") is a proprietary multi-paradigm programming language and numeric computing environment developed by MathWorks. MATLAB allows matrix manipulations, plotting of functions and data, implementation ...
or
SystemC and converted to
RTL designs through
high-level synthesis
High-level synthesis (HLS), sometimes referred to as C synthesis, electronic system-level (ESL) synthesis, algorithmic synthesis, or behavioral synthesis, is an automated design process that takes an abstract behavioral specification of a digital ...
(HLS) tools such as
C to HDL
C to HDL tools convert C language or C-like computer code into a hardware description language (HDL) such as VHDL or Verilog. The converted code can then be synthesized and translated into a hardware device such as a field-programmable gate arr ...
or
flow to HDL
Flow to HDL tools and methods convert flow-based system design into a hardware description language (HDL) such as VHDL or Verilog. Typically this is a method of creating designs for field-programmable gate array, application-specific integrated ci ...
. HLS products called "algorithmic synthesis" allow designers to use C++ to model and synthesize system, circuit, software and verification levels all in one high level language commonly known to
computer engineers
Computer engineering (CoE or CpE) is a branch of electrical engineering and computer science that integrates several fields of computer science and electronic engineering required to develop computer hardware and software. Computer engineers ...
in a manner independent of time scales, which are typically specified in HDL. Other components can remain software and be compiled and embedded onto
soft-core processors included in the SoC as modules in HDL as
IP cores.
Once the
architecture
Architecture is the art and technique of designing and building, as distinguished from the skills associated with construction. It is both the process and the product of sketching, conceiving, planning, designing, and constructing building ...
of the SoC has been defined, any new hardware elements are written in an abstract
hardware description language
In computer engineering, a hardware description language (HDL) is a specialized computer language used to describe the structure and behavior of electronic circuits, and most commonly, digital logic circuits.
A hardware description language e ...
termed
register transfer level
In digital circuit design, register-transfer level (RTL) is a design abstraction which models a synchronous digital circuit in terms of the flow of digital signals (data) between hardware registers, and the logical operations performed on those ...
(RTL) which defines the circuit behavior, or synthesized into RTL from a high level language through high-level synthesis. These elements are connected together in a hardware description language to create the full SoC design. The logic specified to connect these components and convert between possibly different interfaces provided by different vendors is called
glue logic
In electronics, glue logic is the custom logic circuitry used to interface a number of off-the-shelf integrated circuits. This is often achieved using common, inexpensive 7400- or 4000-series components. In more complex cases, a programmable lo ...
.
Design verification
Chips are verified for validation correctness before being sent to a
semiconductor foundry
In the microelectronics industry, a semiconductor fabrication plant (commonly called a fab; sometimes foundry) is a factory where devices such as integrated circuits are manufactured.
Fabs require many expensive devices to function. Estimates ...
. This process is called
functional verification
In electronic design automation, functional verification is the task of verifying that the logic design conforms to specification. Functional verification attempts to answer the question "Does this proposed design do what is intended?" This is a ...
and it accounts for a significant portion of the time and energy expended in the
chip design life cycle, often quoted as 70%.
EE Times
''EE Times'' (''Electronic Engineering Times'') is an electronics industry magazine published in the United States since 1972. EE Times is currently owned by AspenCore, a division of Arrow Electronics since August 2016.
Since its acquisition ...
.
Is verification really 70 percent?
" June 14, 2004. Retrieved July 28, 2015. With the growing complexity of chips,
hardware verification language
A hardware verification language, or HVL, is a programming language used to verify the designs of electronic circuits written in a hardware description language. HVLs typically include features of a high-level programming language like C++ or Java ...
s like
SystemVerilog
SystemVerilog, standardized as IEEE 1800, is a hardware description and hardware verification language used to model, design, simulate, test and implement electronic systems. SystemVerilog is based on Verilog and some extensions, and since 200 ...
,
SystemC,
e, and
OpenVera
OpenVera was a hardware verification language developed by System Science and acquired by Synopsys.
See also
* e (verification language)
* SystemVerilog
SystemVerilog, standardized as IEEE 1800, is a hardware description and hardware veri ...
are being used.
Bugs found in the verification stage are reported to the designer.
Traditionally, engineers have employed simulation acceleration,
emulation
Emulation may refer to:
*Emulation (computing), imitation of behavior of a computer or other electronic system with the help of another type of system
:*Video game console emulator, software which emulates video game consoles
*Gaussian process em ...
or prototyping on
reprogrammable hardware to verify and debug hardware and software for SoC designs prior to the finalization of the design, known as
tape-out
In electronics and photonics design, tape-out or tapeout is the final result of the design process for integrated circuits or printed circuit boards before they are sent for manufacturing. The tapeout is specifically the point at which the graphic ...
.
Field-programmable gate array
A field-programmable gate array (FPGA) is an integrated circuit designed to be configured by a customer or a designer after manufacturinghence the term '' field-programmable''. The FPGA configuration is generally specified using a hardware d ...
s (FPGAs) are favored for prototyping SoCs because
FPGA prototypes are reprogrammable, allow
debugging
In computer programming and software development, debugging is the process of finding and resolving '' bugs'' (defects or problems that prevent correct operation) within computer programs, software, or systems.
Debugging tactics can involve in ...
and are more flexible than
application-specific integrated circuit
An application-specific integrated circuit (ASIC ) is an integrated circuit (IC) chip customized for a particular use, rather than intended for general-purpose use, such as a chip designed to run in a digital voice recorder or a high-efficie ...
s (ASICs).
With high capacity and fast compilation time, simulation acceleration and emulation are powerful technologies that provide wide visibility into systems. Both technologies, however, operate slowly, on the order of MHz, which may be significantly slower – up to 100 times slower – than the SoC's operating frequency. Acceleration and emulation boxes are also very large and expensive at over US$1 million.
FPGA prototypes, in contrast, use FPGAs directly to enable engineers to validate and test at, or close to, a system's full operating frequency with real-world stimuli. Tools such as Certus are used to insert probes in the FPGA RTL that make signals available for observation. This is used to debug hardware, firmware and software interactions across multiple FPGAs with capabilities similar to a logic analyzer.
In parallel, the hardware elements are grouped and passed through a process of
logic synthesis
In computer engineering, logic synthesis is a process by which an abstract specification of desired circuit behavior, typically at register transfer level (RTL), is turned into a design implementation in terms of logic gates, typically by a compu ...
, during which performance constraints, such as operational frequency and expected signal delays, are applied. This generates an output known as a
netlist
In electronic design, a netlist is a description of the connectivity of an electronic circuit. In its simplest form, a netlist consists of a list of the electronic components in a circuit and a list of the nodes they are connected to. A network ...
describing the design as a physical circuit and its interconnections. These netlists are combined with the
glue logic
In electronics, glue logic is the custom logic circuitry used to interface a number of off-the-shelf integrated circuits. This is often achieved using common, inexpensive 7400- or 4000-series components. In more complex cases, a programmable lo ...
connecting the components to produce the schematic description of the SoC as a circuit which can be
printed
Printing is a process for mass reproducing text and images using a master form or template. The earliest non-paper products involving printing include cylinder seals and objects such as the Cyrus Cylinder and the Cylinders of Nabonidus. The ea ...
onto a chip. This process is known as
place and route
Place and route is a stage in the design of printed circuit boards, integrated circuits, and field-programmable gate arrays. As implied by the name, it is composed of two steps, placement and routing. The first step, placement, involves deciding ...
and precedes
tape-out
In electronics and photonics design, tape-out or tapeout is the final result of the design process for integrated circuits or printed circuit boards before they are sent for manufacturing. The tapeout is specifically the point at which the graphic ...
in the event that the SoCs are produced as
application-specific integrated circuit
An application-specific integrated circuit (ASIC ) is an integrated circuit (IC) chip customized for a particular use, rather than intended for general-purpose use, such as a chip designed to run in a digital voice recorder or a high-efficie ...
s (ASIC).
Optimization goals
SoCs must optimize
power use, area on
die
Die, as a verb, refers to death, the cessation of life.
Die may also refer to:
Games
* Die, singular of dice, small throwable objects used for producing random numbers
Manufacturing
* Die (integrated circuit), a rectangular piece of a semicondu ...
, communication, positioning for
locality
Locality may refer to:
* Locality (association), an association of community regeneration organizations in England
* Locality (linguistics)
* Locality (settlement)
* Suburbs and localities (Australia), in which a locality is a geographic subdivis ...
between modular units and other factors. Optimization is necessarily a design goal of SoCs. If optimization was not necessary, the engineers would use a
multi-chip module
A multi-chip module (MCM) is generically an electronic assembly (such as a package with a number of conductor terminals or "pins") where multiple integrated circuits (ICs or "chips"), semiconductor dies and/or other discrete components are int ...
architecture without accounting for the area use, power consumption or performance of the system to the same extent.
Common optimization targets for SoC designs follow, with explanations of each. In general, optimizing any of these quantities may be a hard
combinatorial optimization
Combinatorial optimization is a subfield of mathematical optimization that consists of finding an optimal object from a finite set of objects, where the set of feasible solutions is discrete or can be reduced to a discrete set. Typical combi ...
problem, and can indeed be
NP-hard
In computational complexity theory, NP-hardness ( non-deterministic polynomial-time hardness) is the defining property of a class of problems that are informally "at least as hard as the hardest problems in NP". A simple example of an NP-hard pr ...
fairly easily. Therefore, sophisticated
optimization algorithm
Mathematical optimization (alternatively spelled ''optimisation'') or mathematical programming is the selection of a best element, with regard to some criterion, from some set of available alternatives. It is generally divided into two subfi ...
s are often required and it may be practical to use
approximation algorithm
In computer science and operations research, approximation algorithms are efficient algorithms that find approximate solutions to optimization problems (in particular NP-hard problems) with provable guarantees on the distance of the returned solu ...
s or
heuristics
A heuristic (; ), or heuristic technique, is any approach to problem solving or self-discovery that employs a practical method that is not guaranteed to be optimal, perfect, or rational, but is nevertheless sufficient for reaching an immediate, ...
in some cases. Additionally, most SoC designs contain
multiple variables to optimize simultaneously, so
Pareto efficient
Pareto efficiency or Pareto optimality is a situation where no action or allocation is available that makes one individual better off without making another worse off. The concept is named after Vilfredo Pareto (1848–1923), Italian civil engin ...
solutions are sought after in SoC design. Oftentimes the goals of optimizing some of these quantities are directly at odds, further adding complexity to design optimization of SoCs and introducing
trade-offs in system design.
For broader coverage of trade-offs and
requirements analysis
In systems engineering and software engineering, requirements analysis focuses on the tasks that determine the needs or conditions to meet the new or altered product or project, taking account of the possibly conflicting requirements of the ...
, see
requirements engineering
Requirements engineering (RE) is the process of defining, documenting, and maintaining requirements in the engineering design process. It is a common role in systems engineering and software engineering.
The first use of the term ''requirement ...
.
Targets
Power consumption
SoCs are optimized to minimize the
electrical power
Electric power is the rate at which electrical energy is transferred by an electric circuit. The SI unit of power is the watt, one joule per second. Standard prefixes apply to watts as with other SI units: thousands, millions and billions of ...
used to perform the SoC's functions. Most SoCs must use low power. SoC systems often require long
battery life
An electric battery is a source of electric power consisting of one or more electrochemical cells with external connections for powering Electricity, electrical devices.
When a battery is supplying power, its positive terminal is the cathode a ...
(such as
smartphone
A smartphone is a portable computer device that combines mobile telephone and computing functions into one unit. They are distinguished from feature phones by their stronger hardware capabilities and extensive mobile operating systems, whic ...
s), can potentially spend months or years without a power source while needing to maintain autonomous function, and often are limited in power use by a high number of
embedded SoCs being
networked together in an area. Additionally, energy costs can be high and conserving energy will reduce the
total cost of ownership
Total cost of ownership (TCO) is a financial estimate intended to help buyers and owners determine the direct and indirect costs of a product or service. It is a management accounting concept that can be used in full cost accounting or even ecolog ...
of the SoC. Finally,
waste heat
Waste heat is heat that is produced by a machine, or other process that uses energy, as a byproduct of doing work. All such processes give off some waste heat as a fundamental result of the laws of thermodynamics. Waste heat has lower utility ...
from high energy consumption can damage other circuit components if too much heat is dissipated, giving another pragmatic reason to conserve energy. The amount of energy used in a circuit is the
integral
In mathematics
Mathematics is an area of knowledge that includes the topics of numbers, formulas and related structures, shapes and the spaces in which they are contained, and quantities and their changes. These topics are represented i ...
of
power
Power most often refers to:
* Power (physics), meaning "rate of doing work"
** Engine power, the power put out by an engine
** Electric power
* Power (social and political), the ability to influence people or events
** Abusive power
Power may a ...
consumed with respect to time, and the
average rate of power consumption is the product of
current
Currents, Current or The Current may refer to:
Science and technology
* Current (fluid), the flow of a liquid or a gas
** Air current, a flow of air
** Ocean current, a current in the ocean
*** Rip current, a kind of water current
** Current (stre ...
by
voltage
Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to m ...
. Equivalently, by
Ohm's law
Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points. Introducing the constant of proportionality, the resistance, one arrives at the usual mathematical equat ...
, power is current squared times resistance or voltage squared divided by
resistance
Resistance may refer to:
Arts, entertainment, and media Comics
* Either of two similarly named but otherwise unrelated comic book series, both published by Wildstorm:
** ''Resistance'' (comics), based on the video game of the same title
** ''T ...
:
SoCs are frequently embedded in
portable devices such as
smartphones
A smartphone is a portable computer device that combines mobile telephone and computing functions into one unit. They are distinguished from feature phones by their stronger hardware capabilities and extensive mobile operating systems, which ...
,
GPS navigation device
A satellite navigation device (satnav device) is a user equipment that uses one or more of several global navigation satellite systems (GNSS) to calculate the device's geographical position and provide navigational advice.
Depending on the s ...
s, digital
watches
A watch is a portable timepiece intended to be carried or worn by a person. It is designed to keep a consistent movement despite the motions caused by the person's activities. A wristwatch is designed to be worn around the wrist, attached by ...
(including
smartwatch
A smartwatch is a wearable computer in the form of a watch; modern smartwatches provide a local touchscreen interface for daily use, while an associated smartphone app provides management and telemetry, such as long-term biomonitoring. While ea ...
es) and
netbook
Netbook was a commonly used term that identified a product class of small and inexpensive laptops which were sold from 2007 to around 2013. These machines were designed primarily as cost-effective tools for consumers to access the Inte ...
s. Customers want long battery lives for
mobile computing
Mobile computing is human–computer interaction in which a computer is expected to be transported during normal usage, which allows for the transmission of data, voice, and video. Mobile computing involves mobile communication, mobile hardware ...
devices, another reason that power consumption must be minimized in SoCs.
Multimedia application
Multimedia is a form of communication that uses a combination of different content forms such as text, audio, images, animations, or video into a single interactive presentation, in contrast to tradition ...
s are often executed on these devices, including video games,
video streaming
Video on demand (VOD) is a media distribution system that allows users to access videos without a traditional video playback device and the constraints of a typical static broadcasting schedule. In the 20th century, broadcasting in the form of o ...
,
image processing
An image is a visual representation of something. It can be two-dimensional, three-dimensional, or somehow otherwise feed into the visual system to convey information. An image can be an artifact, such as a photograph or other two-dimensiona ...
; all of which have grown in
computational complexity
In computer science, the computational complexity or simply complexity of an algorithm is the amount of resources required to run it. Particular focus is given to computation time (generally measured by the number of needed elementary operations) ...
in recent years with user demands and expectations for higher-
quality
Quality may refer to:
Concepts
*Quality (business), the ''non-inferiority'' or ''superiority'' of something
*Quality (philosophy), an attribute or a property
*Quality (physics), in response theory
*Energy quality, used in various science discipli ...
multimedia. Computation is more demanding as expectations move towards
3D video
3D films are motion pictures made to give an illusion of three-dimensional solidity, usually with the help of special glasses worn by viewers. They have existed in some form since 1915, but had been largely relegated to a niche in the motion pict ...
at
high resolution
Image resolution is the detail an image holds. The term applies to digital images, film images, and other types of images. "Higher resolution" means more image detail.
Image resolution can be measured in various ways. Resolution quantifies how cl ...
with
multiple standards, so SoCs performing multimedia tasks must be computationally capable platform while being low power to run off a standard mobile battery.
Performance per watt
SoCs are optimized to maximize
power efficiency
In computing, performance per watt is a measure of the energy efficiency of a particular computer architecture or computer hardware. Literally, it measures the rate of computation that can be delivered by a computer for every watt of power consume ...
in performance per watt: maximize the performance of the SoC given a budget of power usage. Many applications such as
edge computing,
distributed processing
A distributed system is a system whose components are located on different networked computers, which communicate and coordinate their actions by passing messages to one another from any system. Distributed computing is a field of computer sci ...
and
ambient intelligence
In computing, ambient intelligence (AmI) refers to electronic environments that are sensitive and responsive to the presence of people. Ambient intelligence was a projection on the future of consumer electronics, telecommunications and computing ...
require a certain level of
computational performance, but power is limited in most SoC environments. The
ARM architecture
ARM (stylised in lowercase as arm, formerly an acronym for Advanced RISC Machines and originally Acorn RISC Machine) is a family of reduced instruction set computer (RISC) instruction set architectures for computer processors, configured ...
has greater performance per watt than
x86
x86 (also known as 80x86 or the 8086 family) is a family of complex instruction set computer (CISC) instruction set architectures initially developed by Intel based on the Intel 8086 microprocessor and its 8088 variant. The 8086 was introd ...
in embedded systems, so it is preferred over x86 for most SoC applications requiring an
embedded processor
An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is ''embedded'' as ...
.
Waste heat
SoC designs are optimized to minimize
waste heat
Waste heat is heat that is produced by a machine, or other process that uses energy, as a byproduct of doing work. All such processes give off some waste heat as a fundamental result of the laws of thermodynamics. Waste heat has lower utility ...
output
Output may refer to:
* The information produced by a computer, see Input/output
* An output state of a system, see state (computer science)
* Output (economics), the amount of goods and services produced
** Gross output in economics, the value of ...
on the chip. As with other
integrated circuit
An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...
s, heat generated due to high
power density
Power density is the amount of power (time rate of energy transfer) per unit volume.
In energy transformers including batteries, fuel cells, motors, power supply units etc., power density refers to a volume, where it is often called volume p ...
are the
bottleneck
Bottleneck literally refers to the narrowed portion (neck) of a bottle
A bottle is a narrow-necked container made of an impermeable material (such as glass, plastic or aluminium) in various shapes and sizes that stores and transports liquids ...
to further
miniaturization
Miniaturization ( Br.Eng.: ''Miniaturisation'') is the trend to manufacture ever smaller mechanical, optical and electronic products and devices. Examples include miniaturization of mobile phones, computers and vehicle engine downsizing. In ele ...
of components.
The power densities of high speed integrated circuits, particularly microprocessors and including SoCs, have become highly uneven. Too much waste heat can damage circuits and erode
reliability
Reliability, reliable, or unreliable may refer to:
Science, technology, and mathematics Computing
* Data reliability (disambiguation), a property of some disk arrays in computer storage
* High availability
* Reliability (computer networking), a ...
of the circuit over time. High temperatures and thermal stress negatively impact reliability,
stress migration Stress migration is a failure mechanism that often occurs in integrated circuit metallization (aluminum, copper). Voids form as result of vacancy migration driven by the hydrostatic
Fluid statics or hydrostatics is the branch of fluid mechanic ...
, decreased
mean time between failures
Mean time between failures (MTBF) is the predicted elapsed time between inherent failures of a mechanical or electronic system during normal system operation. MTBF can be calculated as the arithmetic mean (average) time between failures of a system ...
,
electromigration
Electromigration is the transport of material caused by the gradual movement of the ions in a conductor due to the momentum transfer between conducting electrons and diffusing metal atoms. The effect is important in applications where high direc ...
,
wire bonding
Wire bonding is the method of making interconnections between an integrated circuit (IC) or other semiconductor device and its packaging during semiconductor device fabrication. Although less common, wire bonding can be used to connect an IC ...
,
metastability
In chemistry and physics, metastability denotes an intermediate Energy level, energetic state within a dynamical system other than the system's ground state, state of least energy.
A ball resting in a hollow on a slope is a simple example of me ...
and other performance degradation of the SoC over time.
In particular, most SoCs are in a small physical area or volume and therefore the effects of waste heat are compounded because there is little room for it to diffuse out of the system. Because of high
transistor count
The transistor count is the number of transistors in an electronic device (typically on a single substrate or "chip"). It is the most common measure of integrated circuit complexity (although the majority of transistors in modern microprocessors ...
s on modern devices, oftentimes a layout of sufficient throughput and high
transistor density
The transistor count is the number of transistors in an electronic device (typically on a single substrate or "chip"). It is the most common measure of integrated circuit complexity (although the majority of transistors in modern microprocessors ...
is physically realizable from
fabrication processes but would result in unacceptably high amounts of heat in the circuit's volume.
These thermal effects force SoC and other chip designers to apply conservative
design margin
In engineering, a factor of safety (FoS), also known as (and used interchangeably with) safety factor (SF), expresses how much stronger a system is than it needs to be for an intended load. Safety factors are often calculated using detailed analy ...
s, creating less performant devices to mitigate the risk of
catastrophic failure
A catastrophic failure is a sudden and total failure from which recovery is impossible. Catastrophic failures often lead to cascading systems failure. The term is most commonly used for structural failures, but has often been extended to many oth ...
. Due to increased
transistor densities as length scales get smaller, each
process generation produces more heat output than the last. Compounding this problem, SoC architectures are usually heterogeneous, creating spatially inhomogeneous
heat flux
Heat flux or thermal flux, sometimes also referred to as ''heat flux density'', heat-flow density or ''heat flow rate intensity'' is a flow of energy per unit area per unit time. In SI its units are watts per square metre (W/m2). It has both a ...
es, which cannot be effectively mitigated by uniform
passive cooling
Passive cooling is a building design approach that focuses on heat gain control and heat dissipation in a building in order to improve the indoor thermal comfort with low or no energy consumption. This approach works either by preventing heat from ...
.
Throughput
SoCs are optimized to maximize computational and communications
throughput
Network throughput (or just throughput, when in context) refers to the rate of message delivery over a communication channel, such as Ethernet or packet radio, in a communication network. The data that these messages contain may be delivered ov ...
.
Latency
SoCs are optimized to minimize
latency for some or all of their functions. This can be accomplished by
laying out elements with proper proximity and
locality
Locality may refer to:
* Locality (association), an association of community regeneration organizations in England
* Locality (linguistics)
* Locality (settlement)
* Suburbs and localities (Australia), in which a locality is a geographic subdivis ...
to each-other to minimize the interconnection delays and maximize the speed at which data is communicated between modules,
functional units and memories. In general, optimizing to minimize latency is an
NP-complete
In computational complexity theory, a problem is NP-complete when:
# it is a problem for which the correctness of each solution can be verified quickly (namely, in polynomial time) and a brute-force search algorithm can find a solution by tryi ...
problem equivalent to the
boolean satisfiability problem
In logic and computer science, the Boolean satisfiability problem (sometimes called propositional satisfiability problem and abbreviated SATISFIABILITY, SAT or B-SAT) is the problem of determining if there exists an interpretation that satisfie ...
.
For
tasks running on processor cores, latency and throughput can be improved with
task scheduling
In computing, scheduling is the action of assigning ''resources'' to perform ''tasks''. The ''resources'' may be processors, network links or expansion cards. The ''tasks'' may be threads, processes or data flows.
The scheduling activity is c ...
. Some tasks run in application-specific hardware units, however, and even task scheduling may not be sufficient to optimize all software-based tasks to meet timing and throughput constraints.
Methodologies
Systems on chip are modeled with standard hardware
verification and validation
Verification and validation (also abbreviated as V&V) are independent procedures that are used together for checking that a product, service, or system meets requirements and specifications and that it fulfills its intended purpose. These are ...
techniques, but additional techniques are used to model and optimize SoC design alternatives to make the system optimal with respect to
multiple-criteria decision analysis
Multiple-criteria decision-making (MCDM) or multiple-criteria decision analysis (MCDA) is a sub-discipline of operations research that explicitly evaluates multiple conflicting criteria in decision making (both in daily life and in settings ...
on the above optimization targets.
Task scheduling
Task scheduling
In computing, scheduling is the action of assigning ''resources'' to perform ''tasks''. The ''resources'' may be processors, network links or expansion cards. The ''tasks'' may be threads, processes or data flows.
The scheduling activity is c ...
is an important activity in any computer system with multiple
processes or
threads sharing a single processor core. It is important to reduce and increase for
embedded software
Embedded software is computer software, written to control machines or devices that are not typically thought of as computers, commonly known as embedded systems. It is typically specialized for the particular hardware that it runs on and has time ...
running on an SoC's . Not every important computing activity in a SoC is performed in software running on on-chip processors, but scheduling can drastically improve performance of software-based tasks and other tasks involving
shared resource
In computing, a shared resource, or network share, is a System resource, computer resource made available from one Host (network), host to other hosts on a computer network.
It is a device or piece of information on a computer that can be remot ...
s.
SoCs often schedule tasks according to
network scheduling
A network scheduler, also called packet scheduler, queueing discipline (qdisc) or queueing algorithm, is an Arbiter (electronics), arbiter on a Node (networking), node in a packet switching communication network. It manages the sequence of netwo ...
and
randomized scheduling algorithms.
Pipelining
Hardware and software tasks are often pipelined in
processor design
Processor design is a subfield of computer engineering and electronics engineering (fabrication) that deals with creating a processor, a key component of computer hardware.
The design process involves choosing an instruction set and a certain exe ...
. Pipelining is an important principle for
speedup
In computer architecture, speedup is a number that measures the relative performance of two systems processing the same problem. More technically, it is the improvement in speed of execution of a task executed on two similar architectures with d ...
in
computer architecture
In computer engineering, computer architecture is a description of the structure of a computer system made from component parts. It can sometimes be a high-level description that ignores details of the implementation. At a more detailed level, t ...
. They are frequently used in
GPU
A graphics processing unit (GPU) is a specialized electronic circuit designed to manipulate and alter memory to accelerate the creation of images in a frame buffer intended for output to a display device. GPUs are used in embedded systems, mobil ...
s (
graphics pipeline
In computer graphics, a computer graphics pipeline, rendering pipeline or simply graphics pipeline, is a conceptual model that describes what steps a graphics system needs to perform to Rendering (computer graphics), render a ...
) and RISC processors (evolutions of the
classic RISC pipeline
In the history of computing hardware, history of computer hardware, some early reduced instruction set computer central processing units (RISC CPUs) used a very similar architectural solution, now called a classic RISC pipeline. Those CPUs were: ...
), but are also applied to application-specific tasks such as
digital signal processing
Digital signal processing (DSP) is the use of digital processing, such as by computers or more specialized digital signal processors, to perform a wide variety of signal processing operations. The digital signals processed in this manner are ...
and multimedia manipulations in the context of SoCs.
Probabilistic modeling
SoCs are often analyzed though
probabilistic model
A statistical model is a mathematical model that embodies a set of statistical assumptions concerning the generation of sample data (and similar data from a larger population). A statistical model represents, often in considerably idealized form, ...
s, and
Markov chain
A Markov chain or Markov process is a stochastic model describing a sequence of possible events in which the probability of each event depends only on the state attained in the previous event. Informally, this may be thought of as, "What happe ...
s. For instance,
Little's law allows SoC states and NoC buffers to be modeled as arrival processes and analyzed through
Poisson random variable
In probability theory and statistics, the Poisson distribution is a discrete probability distribution that expresses the probability of a given number of events occurring in a fixed interval of time or space if these events occur with a known co ...
s and
Poisson process
In probability, statistics and related fields, a Poisson point process is a type of random mathematical object that consists of points randomly located on a mathematical space with the essential feature that the points occur independently of one ...
es.
Markov chains
SoCs are often modeled with
Markov chain
A Markov chain or Markov process is a stochastic model describing a sequence of possible events in which the probability of each event depends only on the state attained in the previous event. Informally, this may be thought of as, "What happe ...
s, both
discrete time
In mathematical dynamics, discrete time and continuous time are two alternative frameworks within which variables that evolve over time are modeled.
Discrete time
Discrete time views values of variables as occurring at distinct, separate "po ...
and
continuous time
In mathematical dynamics, discrete time and continuous time are two alternative frameworks within which variables that evolve over time are modeled.
Discrete time
Discrete time views values of variables as occurring at distinct, separate "po ...
variants. Markov chain modeling allows
asymptotic analysis
In mathematical analysis, asymptotic analysis, also known as asymptotics, is a method of describing limiting behavior.
As an illustration, suppose that we are interested in the properties of a function as becomes very large. If , then as beco ...
of the SoC's
steady state distribution of power, heat, latency and other factors to allow design decisions to be optimized for the common case.
Fabrication
SoC chips are typically
fabricated using
metal–oxide–semiconductor
The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which d ...
(MOS) technology. The netlists described above are used as the basis for the physical design (
place and route
Place and route is a stage in the design of printed circuit boards, integrated circuits, and field-programmable gate arrays. As implied by the name, it is composed of two steps, placement and routing. The first step, placement, involves deciding ...
) flow to convert the designers' intent into the design of the SoC. Throughout this conversion process, the design is analyzed with static timing modeling, simulation and other tools to ensure that it meets the specified operational parameters such as frequency, power consumption and dissipation, functional integrity (as described in the register transfer level code) and electrical integrity.
When all known bugs have been rectified and these have been re-verified and all physical design checks are done, the physical design files describing each layer of the chip are sent to the foundry's mask shop where a full set of glass lithographic masks will be etched. These are sent to a wafer fabrication plant to create the SoC dice before packaging and testing.
SoCs can be fabricated by several technologies, including:
*
Full custom
Full-custom design is a methodology for designing integrated circuits by specifying the layout of each individual transistor and the interconnections between them. Alternatives to full-custom design include various forms of semi-custom design, su ...
ASIC
An application-specific integrated circuit (ASIC ) is an integrated circuit (IC) chip customized for a particular use, rather than intended for general-purpose use, such as a chip designed to run in a digital voice recorder or a high-efficien ...
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Standard cell
In semiconductor design, standard cell methodology is a method of designing application-specific integrated circuits (ASICs) with mostly digital-logic features. Standard cell methodology is an example of design abstraction, whereby a low-level v ...
ASIC
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Field-programmable gate array
A field-programmable gate array (FPGA) is an integrated circuit designed to be configured by a customer or a designer after manufacturinghence the term '' field-programmable''. The FPGA configuration is generally specified using a hardware d ...
(FPGA)
ASICs consume less power and are faster than FPGAs but cannot be reprogrammed and are expensive to manufacture. FPGA designs are more suitable for lower volume designs, but after enough units of production ASICs reduce the total cost of ownership.
SoC designs consume less power and have a lower cost and higher reliability than the multi-chip systems that they replace. With fewer packages in the system, assembly costs are reduced as well.
However, like most
very-large-scale integration
Very large-scale integration (VLSI) is the process of creating an integrated circuit (IC) by combining millions or billions of MOS transistors onto a single chip. VLSI began in the 1970s when MOS integrated circuit (Metal Oxide Semiconductor) c ...
(VLSI) designs, the total cost is higher for one large chip than for the same functionality distributed over several smaller chips, because of
lower yields and higher
non-recurring engineering
Non-recurring engineering (NRE) cost refers to the one-time cost to research, design, develop and test a new product or product enhancement. When budgeting for a new product, NRE must be considered to analyze if a new product will be profitable. Ev ...
costs.
When it is not feasible to construct an SoC for a particular application, an alternative is a
system in package
A system in a package (SiP) or system-in-package is a number of integrated circuits enclosed in one or more chip carrier packages that may be stacked using package on package. The SiP performs all or most of the functions of an electronic system ...
(SiP) comprising a number of chips in a single
package. When produced in large volumes, SoC is more cost-effective than SiP because its packaging is simpler. Another reason SiP may be preferred is
waste heat
Waste heat is heat that is produced by a machine, or other process that uses energy, as a byproduct of doing work. All such processes give off some waste heat as a fundamental result of the laws of thermodynamics. Waste heat has lower utility ...
may be too high in a SoC for a given purpose because functional components are too close together, and in an SiP heat will dissipate better from different functional modules since they are physically further apart.
Benchmarks
SoC
research and development
Research and development (R&D or R+D), known in Europe as research and technological development (RTD), is the set of innovative activities undertaken by corporations or governments in developing new services or products, and improving existi ...
often compares many options. Benchmarks, such as COSMIC,
are developed to help such evaluations.
See also
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List of system on a chip suppliers
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Post-silicon validation {{no footnotes, date=July 2011
Post-silicon validation and debug is the last step in the development of a semiconductor integrated circuit.
Pre-silicon process
During the pre-silicon process, engineers test devices in a virtual environment with ...
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ARM architecture family
ARM (stylised in lowercase as arm, formerly an acronym for Advanced RISC Machines and originally Acorn RISC Machine) is a family of reduced instruction set computer (RISC) instruction set architectures for central processing unit, computer ...
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Single-board computer
A single-board computer (SBC) is a complete computer built on a single circuit board, with microprocessor(s), memory, input/output (I/O) and other features required of a functional computer. Single-board computers are commonly made as demonstrati ...
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System in a package
A system in a package (SiP) or system-in-package is a number of integrated circuits enclosed in one or more chip carrier packages that may be stacked using package on package. The SiP performs all or most of the functions of an electronic system, ...
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Network on a chip
A network on a chip or network-on-chip (NoC or )This article uses the convention that "NoC" is pronounced . Therefore, it uses the convention "a" for the indefinite article corresponding to NoC ("a NoC"). Other sources may pronounce it as an ...
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Programmable SoC
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Application-specific instruction set processor
An application-specific instruction set processor (ASIP) is a component used in system on a chip design. The instruction set architecture of an ASIP is tailored to benefit a specific application. This specialization of the core provides a tradeo ...
(ASIP)
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Platform-based design
Platform-based design is defined in ''Taxonomies for the Development and Verification of Digital Systems''Brian Bailey, Grant Martin and Thomas Anderson, ''Taxonomies for the Development and Verification of Digital Systems'', Springer (2005) as ...
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Lab-on-a-chip
A lab-on-a-chip (LOC) is a device that integrates one or several laboratory functions on a single integrated circuit (commonly called a "chip") of only millimeters to a few square centimeters to achieve automation and high-throughput screening. ...
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Organ-on-a-chip
An organ-on-a-chip (OOC) is a multi-channel 3-D microfluidic cell culture, integrated circuit (chip) that simulates the activities, mechanics and physiological response of an entire organ or an organ system, a type of artificial organ. It constitu ...
in biomedical technology
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Multi-chip module
A multi-chip module (MCM) is generically an electronic assembly (such as a package with a number of conductor terminals or "pins") where multiple integrated circuits (ICs or "chips"), semiconductor dies and/or other discrete components are int ...
Notes
References
Further reading
* 465 pages.
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External links
SOCCAnnual
IEEE
The Institute of Electrical and Electronics Engineers (IEEE) is a 501(c)(3) professional association for electronic engineering and electrical engineering (and associated disciplines) with its corporate office in New York City and its operation ...
International SoC Conference
Bayafree SoC platform assembly and IP integration tool
Systems on Chip for Embedded Applications Auburn University
Auburn University (AU or Auburn) is a public land-grant research university in Auburn, Alabama. With more than 24,600 undergraduate students and a total enrollment of more than 30,000 with 1,330 faculty members, Auburn is the second largest uni ...
seminar in
VLSI
Very large-scale integration (VLSI) is the process of creating an integrated circuit (IC) by combining millions or billions of MOS transistors onto a single chip. VLSI began in the 1970s when MOS integrated circuit (Metal Oxide Semiconductor) c ...
Instant SoCSoC for FPGAs defined by C++
{{Hardware acceleration
Computer engineering
Electronic design
Microtechnology
Hardware acceleration
Computer systems
Application-specific integrated circuits