A single-core processor is a microprocessor with a single

CPU A central processing unit (CPU), also called a central processor, main processor, or just processor, is the primary processor in a given computer. Its electronic circuitry executes instructions of a computer program, such as arithmetic, log ...

on its die. It performs the

fetch-decode-execute cycle The instruction cycle (also known as the fetch–decode–execute cycle, or simply the fetch–execute cycle) is the cycle that the central processing unit (CPU) follows from boot-up until the computer has shut down in order to process instructions ...

one at a time, as it only runs on one thread. A computer using a single core CPU is generally slower than a multi-core system. Single core processors used to be widespread in desktop computers, but as applications demanded more processing power, the slower speed of single core systems became a detriment to performance. Windows supported single-core processors up until the release of

Windows 11 Windows 11 is a version of Microsoft's Windows NT operating system, released on October 5, 2021, as the successor to Windows 10 (2015). It is available as a free upgrade for devices running Windows 10 that meet the #System requirements, Windo ...

, where a dual-core processor is required. Single core processors are still in use in some niche circumstances. Some older legacy systems like those running antiquated operating systems (e.g.

Windows 98 Windows 98 is a consumer-oriented operating system developed by Microsoft as part of its Windows 9x family of Microsoft Windows operating systems. It was the second operating system in the 9x line, as the successor to Windows 95. It was Software ...

) cannot gain any benefit from multi-core processors. Single core processors are also used in hobbyist computers like 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 collaboration with Broadcom Inc., Broadcom. To commercialize the product and support its growing demand, the ...

and

Single-board microcontroller A single-board microcontroller is a microcontroller built onto a single printed circuit board. This board provides all of the circuitry necessary for a useful control task: a microprocessor, I/O circuits, a clock generator, RAM, stored program ...

s. The production of single-core desktop processors ended in 2013 with the

Celeron Celeron is a series of IA-32 and x86-64 computer microprocessor, microprocessors targeted at low-cost Personal computer, personal computers, manufactured by Intel from 1998 until 2023. The first Celeron-branded CPU was introduced on April 15, ...

G440, G460, G465 & G470.

Development

The first single core processor was the

Intel 4004 The Intel 4004 was part of the 4 chip MCS-4 micro computer set, released by the Intel, Intel Corporation in November 1971; the 4004 being part of the first commercially marketed microprocessor chipset, and the first in a long line of List of I ...

, which was commercially released on November 15, 1971 by

Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California, and Delaware General Corporation Law, incorporated in Delaware. Intel designs, manufactures, and sells computer compo ...

. Since then many improvements have been made to single core processors, going from the 740 kHz of the Intel 4004 to the 2 GHz Celeron G470.

Advantages

* Single core processors draw less power than larger, multi-core processors. * Single core processors can be made a lot more cheaply than multi core systems, meaning they can be used in embedded systems.

Disadvantages

* Single-core processors are generally outperformed by multi-core processors. * Single-core processors are more likely to bottleneck with faster peripheral components, as these components have to wait for the CPU to finish its cycle. * Single-core processors lack parallelisation, meaning only one application can run at once. This reduces performance as other processes have to wait for processor time, leading to process starvation.

Increasing parallel trend

* Single-core one processor on a die. Since about 2012, even most

smartphones A smartphone is a mobile phone with advanced computing capabilities. It typically has a touchscreen interface, allowing users to access a wide range of applications and services, such as web browsing, email, and social media, as well as mult ...

CPUs A central processing unit (CPU), also called a central processor, main processor, or just processor, is the primary Processor (computing), processor in a given computer. Its electronic circuitry executes Instruction (computing), instructions ...

marketed are no longer single-core;

Microcontroller A microcontroller (MC, uC, or μC) or microcontroller unit (MCU) is a small computer on a single integrated circuit. A microcontroller contains one or more CPUs (processor cores) along with memory and programmable input/output peripherals. Pro ...

s are still single-core, while there are exceptions. *

Multi-core processor A multi-core processor (MCP) is a microprocessor on a single integrated circuit (IC) with two or more separate central processing units (CPUs), called ''cores'' to emphasize their multiplicity (for example, ''dual-core'' or ''quad-core''). Ea ...

s a 'few' processors on a die, e.g. 2, 4, 8. *

Manycore processor 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 ...

s a 'large number' of processors on a die, e.g. 10s, 100s, 1000s. Some specialist

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 ...

s/ Accelerators and

GPU A graphics processing unit (GPU) is a specialized electronic circuit designed for digital image processing and to accelerate computer graphics, being present either as a discrete video card or embedded on motherboards, mobile phones, personal ...

s fall into this category.

References

{{CPU technologies Computer architecture Microprocessors Flynn's taxonomy