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Iron Law Of Processor Performance
In computer architecture, the iron law of processor performance (or simply iron law of performance) describes the performance trade-off between complexity and the number of primitive instructions that processors use to perform calculations. This formulation of the trade-off spurred the development of Reduced Instruction Set Computers (RISC) whose instruction set architectures (ISAs) leverage a smaller set of core instructions to improve performance. The term was coined by Douglas Clark based on research performed by Clark and Joel Emer in the 1980s. Explanation The performance of a processor is the time it takes to execute a program: \tfrac. This can be further broken down into three factors: \mathrmSelection of an instruction set architecture affects \mathrm, whereas \mathrm is largely determined by the manufacturing technology. Classic Complex Instruction Set Computer (CISC) ISAs optimized \mathrm by providing a larger set of more complex CPU instructions. Generally spe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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, the description may include the instruction set architecture design, microarchitecture design, logic design, and implementation. History The first documented computer architecture was in the correspondence between Charles Babbage and Ada Lovelace, describing the analytical engine. When building the computer Z1 in 1936, Konrad Zuse described in two patent applications for his future projects that machine instructions could be stored in the same storage used for data, i.e., the stored-program concept. Two other early and important examples are: * John von Neumann's 1945 paper, First Draft of a Report on the EDVAC, which described an organization of logical elements; and *Alan Turing's more detailed ''Proposed Electronic Calculator'' for t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Machine Code
In computer programming, machine code is any low-level programming language, consisting of machine language instructions, which are used to control a computer's central processing unit (CPU). Each instruction causes the CPU to perform a very specific task, such as a load, a store, a jump, or an arithmetic logic unit (ALU) operation on one or more units of data in the CPU's registers or memory. Early CPUs had specific machine code that might break backwards compatibility with each new CPU released. The notion of an instruction set architecture (ISA)Â defines and specifies the behavior and encoding in memory of the instruction set of the system, without specifying its exact implementation. This acts as an abstraction layer, enabling compatibility within the same family of CPUs, so that machine code written or generated according to the ISA for the family will run on all CPUs in the family, including future CPUs. In general, each architecture family (e.g. x86, ARM) has its ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reduced Instruction Set Computer
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 computer (CISC), a RISC computer might require more instructions (more code) in order to accomplish a task because the individual instructions are written in simpler code. The goal is to offset the need to process more instructions by increasing the speed of each instruction, in particular by implementing an instruction pipeline, which may be simpler given simpler instructions. The key operational concept of the RISC computer is that each instruction performs only one function (e.g. copy a value from memory to a register). The RISC computer usually has many (16 or 32) high-speed, general-purpose registers with a load/store architecture in which the code for the register-register instructions (for performing arithmetic and tests) are separate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 ''implementation''. In general, an ISA defines the supported instructions, data types, registers, the hardware support for managing main memory, fundamental features (such as the memory consistency, addressing modes, virtual memory), and the input/output model of a family of implementations of the ISA. An ISA specifies the behavior of machine code running on implementations of that ISA in a fashion that does not depend on the characteristics of that implementation, providing binary compatibility between implementations. This enables multiple implementations of an ISA that differ in characteristics such as performance, physical size, and monetary cost (among other things), but that are capable of running the same machine code, s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Joel Emer
Joel S. Emer (born March 2, 1954) is a pioneer in computer performance analysis techniques and a microprocessor architect. He is currently a researcher at Nvidia, and a Professor of the Practice at MIT, and was formerly an Intel Fellow. He was the 2009 recipient of the Eckert–Mauchly Award, an ACM/ IEEE joint award for contributions to computer and digital systems architecture. Emer received his Ph.D. degree from the University of Illinois, Urbana-Champaign under the supervision of Prof. Edward S. Davidson. His first job immediately after graduation was at Digital Equipment Corporation where he initially worked on VAX performance evaluation and then on Alpha performance evaluation. As a consequence of his performance evaluation work, he became a pioneer in the quantitative approach to computer architecture. In conjunction with the development and application of various performance analysis techniques, he contributed a variety of research and advanced development ideas th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Complex Instruction Set Computer
A complex instruction set computer (CISC ) is a computer architecture in which single instructions can execute several low-level operations (such as a load from memory, an arithmetic operation, and a memory store) or are capable of multi-step operations or addressing modes within single instructions. The term was retroactively coined in contrast to reduced instruction set computer (RISC) and has therefore become something of an umbrella term for everything that is not RISC, where the typical differentiating characteristic is that most RISC designs use uniform instruction length for almost all instructions, and employ strictly separate load and store instructions. Examples of CISC architectures include complex mainframe computers to simplistic microcontrollers where memory load and store operations are not separated from arithmetic instructions. Specific instruction set architectures that have been retroactively labeled CISC are System/360 through z/Architecture, the PDP-11 and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Compressed Instruction Set
A compressed instruction set, or simply compressed instructions, are a variation on a microprocessor's instruction set architecture (ISA) that allows instructions to be represented in a more compact format. In most real-world examples, compressed instructions are 16 bits long in a processor that would otherwise use 32-bit instructions. The 16-bit ISA is a subset of the full 32-bit ISA, not a separate instruction set. The smaller format requires some tradeoffs: generally, there are fewer instructions available, and fewer processor registers can be used. The concept was originally introduced by Hitachi as a way to improve the code density of their SuperH RISC processor design as it moved from 16-bit to 32-bit instructions in the SH-5 version. The new design had two instruction sets, one giving access to the entire ISA of the new design, and a smaller 16-bit set known as SHcompact that allowed programs to run in smaller amounts of main memory. As the memory of even the smallest sys ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Classic RISC Pipeline
In the 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: MIPS, SPARC, Motorola 88000, and later the notional CPU DLX invented for education. Each of these classic scalar RISC designs fetches and tries to execute one instruction per cycle. The main common concept of each design is a five-stage execution instruction pipeline. During operation, each pipeline stage works on one instruction at a time. Each of these stages consists of a set of flip-flops to hold state, and combinational logic that operates on the outputs of those flip-flops. The classic five stage RISC pipeline Instruction fetch The instructions reside in memory that takes one cycle to read. This memory can be dedicated to SRAM, or an Instruction Cache. The term "latency" is used in computer science often and means the time from when an operation starts ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Architecture Statements
A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as programs. These programs enable computers to perform a wide range of tasks. A computer system is a nominally complete computer that includes the hardware, operating system (main software), and peripheral equipment needed and used for full operation. This term may also refer to a group of computers that are linked and function together, such as a computer network or computer cluster. A broad range of industrial and consumer products use computers as control systems. Simple special-purpose devices like microwave ovens and remote controls are included, as are factory devices like industrial robots and computer-aided design, as well as general-purpose devices like personal computers and mobile devices like smartphones. Computers power the Internet, which links ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
