Computer architecture
Encyclopedia
In computer science
and engineering
, computer architecture is the practical art of selecting and interconnecting hardware
components to create computers that meet functional, performance and cost goals and the formal modelling of those systems.
The noun computer architecture or digital computer organization is a blueprint
, a description of the requirements and basic design for the various parts of a computer. It is usually most concerned with how the central processing unit
(CPU) acts and how it accesses computer memory
. Some currently (2011) fashionable computer architectures include cluster computing
and Non-Uniform Memory Access
.
The art of computer architecture has three main subcategories:
The second step of designing a new architecture is often to design a software simulator, and write representative programs in the ISA, to test and adjust the architectural elements. At this stage, it is now commonplace for compiler
designers to collaborate, suggesting improvements in the ISA. Modern simulators normally measure time in clock cycles, and give energy use estimates in watts.
Once the instruction set and microarchitecture are described, a practical machine needs to be designed. This design process is called the implementation. Implementation is usually not considered architectural definition, but rather hardware design engineering.
Implementation can be further broken down into several (not fully distinct) steps:
For CPU
s, the entire implementation process is often called CPU design
.
’s main research center.
Johnson had the opportunity to write a proprietary research communication about Stretch, an IBM-developed supercomputer
for Los Alamos Scientific Laboratory. In attempting to characterize his chosen level of detail for discussing the luxuriously embellished computer, he noted that his description of formats, instruction types, hardware parameters, and speed enhancements was at the level of “system architecture” – a term that seemed more useful than “machine organization.”
Subsequently, Brooks, one of the Stretch designers, started Chapter 2 of a book (Planning a Computer System: Project Stretch, ed. W. Buchholz, 1962) by writing, “Computer architecture, like other architecture, is the art of determining the needs of the user of a structure and then designing to meet those needs as effectively as possible within economic and technological constraints.”
Brooks went on to play a major role in the development of the IBM System/360 (now called the IBM zSeries) line of computers, where “architecture” gained currency as a noun with the definition as “what the user needs to know”. Later the computer world would employ the term in many less-explicit ways.
The quantum computer architecture holds the most promise to revolutionize computing.
It can also be defined as the design of the task-performing part of computers, i.e. how various gates and transistors are interconnected and are caused to function per the instructions given by an assembly language programmer.
Memory organization defines how instructions interact with the memory.
Computer organization also helps plan the selection of a processor for a particular project. Multimedia projects may need very rapid data access, while supervisory software may need fast interrupts.
Sometimes certain tasks need additional components as well. For example, a computer capable of virtualization needs virtual memory
hardware so that the memory of different simulated computers can be kept separated.
The computer organization and features also affect the power consumption and the cost
of the processor.
The most common scheme carefully chooses the bottleneck that most reduces the computer's speed. Ideally, the cost is allocated proportionally to assure that the data rate is nearly the same for all parts of the computer, with the most costly part being the slowest. This is how skillful commercial integrators optimize personal computer
s.
). This metric explicitly measures the efficiency of the architecture at any clock speed. Since a faster clock can make a faster computer, this is a useful, widely applicable measurement. Historic complex instruction set computers had MIPs/MHz as low as 0.1 (See instructions per second
). Simple modern processors easily reach near 1. Superscalar
processors may reach three to five by executing several instructions per clock cycle. Multicore and vector processing CPUs can multiply this further by acting on a lot of data per instruction, and have several CPUs executing in parallel.
Counting machine language instructions would be misleading because they can do varying amounts of work in different ISAs. The "instruction" in the standard measurements is not a count of the ISA's actual machine language instructions, but a historical unit of measurement, usually based on the speed of the VAX
computer architecture.
Historically, many people measured the speed by the clock rate (usually in MHz or GHz). This refers to the cycles per second of the main clock of the CPU. However, this metric is somewhat misleading, as a machine with a higher clock rate may not necessarily have higher performance. As a result manufacturers have moved away from clock speed as a measure of performance.
Computer performance can also be measured with the amount of cache a processor has. If the speed, MHz or GHz, were to be a car then the cache is like the gas tank. No matter how fast the car goes, it will still need to get gas. The higher the speed, and the greater the cache, the faster a processor runs.
Other factors influence speed, such as the mix of functional units, bus
speeds, available memory, and the type and order of instructions in the programs being run.
In a typical home computer, the simplest, most reliable way to speed performance is usually to add random access memory (RAM). More RAM increases the likelihood that needed data or a program will be in RAM. So, the system is less likely to need to move memory data from the disk. The disk is often ten thousand times slower than RAM because it has mechanical parts that must move to access its data.
There are two main types of speed, latency and throughput. Latency is the time between the start of a process and its completion. Throughput is the amount of work done per unit time. Interrupt latency
is the guaranteed maximum response time of the system to an electronic event (e.g. when the disk drive finishes moving some data).
Performance is affected by a very wide range of design choices — for example, pipelining a processor usually makes latency worse (slower) but makes throughput better. Computers that control machinery usually need low interrupt latencies. These computers operate in a real-time
environment and fail if an operation is not completed in a specified amount of time. For example, computer-controlled anti-lock brakes must begin braking within a predictable, short time after the brake pedal is sensed.
The performance of a computer can be measured using other metrics, depending upon its application domain. A system may be CPU bound
(as in numerical calculation), I/O bound (as in a webserving application) or memory bound (as in video editing). Power consumption has become important in servers and portable devices like laptops.
Benchmark
ing tries to take all these factors into account by measuring the time a computer takes to run through a series of test programs. Although benchmarking shows strengths, it may not help one to choose a computer. Often the measured machines split on different measures. For example, one system might handle scientific applications quickly, while another might play popular video games more smoothly. Furthermore, designers have been known to add special features to their products, whether in hardware or software, which permit a specific benchmark to execute quickly but which do not offer similar advantages to other, more general tasks.
With the increasing power density of modern circuits as the number of transistors per chip scales (Moore's law
), power efficiency has increased in importance. Recent processor designs such as the Intel Core 2
put more emphasis on increasing power efficiency. Also, in the world of embedded computing, power efficiency has long been and remains an important goal next to throughput and latency.
Computer science
Computer science or computing science is the study of the theoretical foundations of information and computation and of practical techniques for their implementation and application in computer systems...
and engineering
Computer engineering
Computer engineering, also called computer systems engineering, is a discipline that integrates several fields of electrical engineering and computer science required to develop computer systems. Computer engineers usually have training in electronic engineering, software design, and...
, computer architecture is the practical art of selecting and interconnecting hardware
Computer hardware
Personal computer hardware are component devices which are typically installed into or peripheral to a computer case to create a personal computer upon which system software is installed including a firmware interface such as a BIOS and an operating system which supports application software that...
components to create computers that meet functional, performance and cost goals and the formal modelling of those systems.
The noun computer architecture or digital computer organization is a blueprint
Blueprint
A blueprint is a type of paper-based reproduction usually of a technical drawing, documenting an architecture or an engineering design. More generally, the term "blueprint" has come to be used to refer to any detailed plan....
, a description of the requirements and basic design for the various parts of a computer. It is usually most concerned with how the central processing unit
Central processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
(CPU) acts and how it accesses computer memory
Computer memory
In computing, memory refers to the physical devices used to store programs or data on a temporary or permanent basis for use in a computer or other digital electronic device. The term primary memory is used for the information in physical systems which are fast In computing, memory refers to the...
. Some currently (2011) fashionable computer architectures include cluster computing
Cluster Computing
Cluster Computing: the Journal of Networks, Software Tools and Applications is a journal for parallel processing, distributed computing systems, and computer communication networks....
and Non-Uniform Memory Access
Non-Uniform Memory Access
Non-Uniform Memory Access is a computer memory design used in Multiprocessing, where the memory access time depends on the memory location relative to a processor...
.
The art of computer architecture has three main subcategories:
- Instruction set architectureInstruction setAn instruction set, or instruction set architecture , is the part of the computer architecture related to programming, including the native data types, instructions, registers, addressing modes, memory architecture, interrupt and exception handling, and external I/O...
, or ISA. The ISA is the codeMachine codeMachine code or machine language is a system of impartible instructions executed directly by a computer's central processing unit. Each instruction performs a very specific task, typically either an operation on a unit of data Machine code or machine language is a system of impartible instructions...
that a central processor reads and acts upon. It is the machine language (or assembly languageAssembly languageAn assembly language is a low-level programming language for computers, microprocessors, microcontrollers, and other programmable devices. It implements a symbolic representation of the machine codes and other constants needed to program a given CPU architecture...
), including the instruction setInstruction setAn instruction set, or instruction set architecture , is the part of the computer architecture related to programming, including the native data types, instructions, registers, addressing modes, memory architecture, interrupt and exception handling, and external I/O...
, word size, memory address modesAddressing modeAddressing modes are an aspect of the instruction set architecture in most central processing unit designs. The various addressing modes that are defined in a given instruction set architecture define how machine language instructions in that architecture identify the operand of each instruction...
, processor registerProcessor registerIn computer architecture, a processor register is a small amount of storage available as part of a CPU or other digital processor. Such registers are addressed by mechanisms other than main memory and can be accessed more quickly...
s, and address and data formats.
- MicroarchitectureMicroarchitectureIn computer engineering, microarchitecture , also called computer organization, is the way a given instruction set architecture is implemented on a processor. A given ISA may be implemented with different microarchitectures. Implementations might vary due to different goals of a given design or...
, also known as Computer organization describes the data paths, data processing elements and data storage elements, and describes how they should implement the ISA. The size of a computer's cacheCacheIn computer engineering, a cache is a component that transparently stores data so that future requests for that data can be served faster. The data that is stored within a cache might be values that have been computed earlier or duplicates of original values that are stored elsewhere...
for instance, is an organizational issue that generally has nothing to do with the ISA.
- System Design includes all of the other hardware components within a computing system. These include:
- Data paths, such as computer busComputer busIn computer architecture, a bus is a subsystem that transfers data between components inside a computer, or between computers.Early computer buses were literally parallel electrical wires with multiple connections, but the term is now used for any physical arrangement that provides the same...
es and switches - Memory controllerMemory controllerThe memory controller is a digital circuit which manages the flow of data going to and from the main memory. It can be a separate chip or integrated into another chip, such as on the die of a microprocessor...
s and hierarchies - Data processing other than the CPU, such as direct memory accessDirect memory accessDirect memory access is a feature of modern computers that allows certain hardware subsystems within the computer to access system memory independently of the central processing unit ....
(DMA) - Miscellaneous issues such as virtualizationVirtualizationVirtualization, in computing, is the creation of a virtual version of something, such as a hardware platform, operating system, a storage device or network resources....
or multiprocessingMultiprocessingMultiprocessing is the use of two or more central processing units within a single computer system. The term also refers to the ability of a system to support more than one processor and/or the ability to allocate tasks between them...
.
The second step of designing a new architecture is often to design a software simulator, and write representative programs in the ISA, to test and adjust the architectural elements. At this stage, it is now commonplace for compiler
Compiler
A compiler is a computer program that transforms source code written in a programming language into another computer language...
designers to collaborate, suggesting improvements in the ISA. Modern simulators normally measure time in clock cycles, and give energy use estimates in watts.
Once the instruction set and microarchitecture are described, a practical machine needs to be designed. This design process is called the implementation. Implementation is usually not considered architectural definition, but rather hardware design engineering.
Implementation can be further broken down into several (not fully distinct) steps:
- Logic Implementation — design of blocks defined in the microarchitecture at (primarily) the register-transfer level and logic gateLogic gateA logic gate is an idealized or physical device implementing a Boolean function, that is, it performs a logical operation on one or more logic inputs and produces a single logic output. Depending on the context, the term may refer to an ideal logic gate, one that has for instance zero rise time and...
level. - Circuit Implementation — transistorTransistorA transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
-level design of basic elements (gates, multiplexers, latches etc.) as well as of some larger blocks (ALUArithmetic logic unitIn computing, an arithmetic logic unit is a digital circuit that performs arithmetic and logical operations.The ALU is a fundamental building block of the central processing unit of a computer, and even the simplest microprocessors contain one for purposes such as maintaining timers...
s, caches etc.) that may be implemented at this level, or even (partly) at the physical level, for performance reasons. - Physical Implementation — physical circuits are drawn out, the different circuit components are placed in a chip floorplanFloorplan (microelectronics)In electronic design automation, a floorplan of an integrated circuit is a schematic representation of tentative placement of its major functional blocks....
or on a board and the wires connecting them are routed. - Design Validation — The computer as a whole is tested to see if it works in all situations and all timings. Once implementation starts, the first design validations are simulations using logic emulators. However, this is usually too slow to run realistic programs. So, after making corrections, next, prototypes are constructed using field-programmable gate-arrays FPGAs. Many hobby projects stop at this stage. The final step is to test prototype integrated circuits. Integrated circuits may have to be redesigned several times to fix problems.
For CPU
Central processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
s, the entire implementation process is often called CPU design
CPU design
CPU design is the design engineering task of creating a central processing unit , a component of computer hardware. It is a subfield of electronics engineering and computer engineering.- Overview :CPU design focuses on these areas:...
.
History
The term “architecture” in computer literature can be traced to the work of Lyle R. Johnson, Muhammad Usman Khan and Frederick P. Brooks, Jr., members in 1959 of the Machine Organization department in IBMIBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
’s main research center.
Johnson had the opportunity to write a proprietary research communication about Stretch, an IBM-developed supercomputer
Supercomputer
A supercomputer is a computer at the frontline of current processing capacity, particularly speed of calculation.Supercomputers are used for highly calculation-intensive tasks such as problems including quantum physics, weather forecasting, climate research, molecular modeling A supercomputer is a...
for Los Alamos Scientific Laboratory. In attempting to characterize his chosen level of detail for discussing the luxuriously embellished computer, he noted that his description of formats, instruction types, hardware parameters, and speed enhancements was at the level of “system architecture” – a term that seemed more useful than “machine organization.”
Subsequently, Brooks, one of the Stretch designers, started Chapter 2 of a book (Planning a Computer System: Project Stretch, ed. W. Buchholz, 1962) by writing, “Computer architecture, like other architecture, is the art of determining the needs of the user of a structure and then designing to meet those needs as effectively as possible within economic and technological constraints.”
Brooks went on to play a major role in the development of the IBM System/360 (now called the IBM zSeries) line of computers, where “architecture” gained currency as a noun with the definition as “what the user needs to know”. Later the computer world would employ the term in many less-explicit ways.
Computer architectures
There are many types of computer architectures:- Quantum computerQuantum computerA quantum computer is a device for computation that makes direct use of quantum mechanical phenomena, such as superposition and entanglement, to perform operations on data. Quantum computers are different from traditional computers based on transistors...
vs Chemical computerChemical computerA chemical computer, also called reaction-diffusion computer, BZ computer or gooware computer is an unconventional computer based on a semi-solid chemical "soup" where data is represented by varying concentrations of chemicals. The computations are performed by naturally occurring chemical... - Scalar processorScalar processorScalar processors represent the simplest class of computer processors. A scalar processor processes one datum at a time . , a scalar processor is classified as a SISD processor .In a vector processor, by contrast, a single instruction operates simultaneously on multiple data items...
vs Vector processorVector processorA vector processor, or array processor, is a central processing unit that implements an instruction set containing instructions that operate on one-dimensional arrays of data called vectors. This is in contrast to a scalar processor, whose instructions operate on single data items... - Non-Uniform Memory AccessNon-Uniform Memory AccessNon-Uniform Memory Access is a computer memory design used in Multiprocessing, where the memory access time depends on the memory location relative to a processor...
(NUMA) computers - Register machineRegister machineIn mathematical logic and theoretical computer science a register machine is a generic class of abstract machines used in a manner similar to a Turing machine...
vs Stack machineStack machineA stack machine may be* A real or emulated computer that evaluates each sub-expression of a program statement via a pushdown data stack and uses a reverse Polish notation instruction set.... - Harvard architectureHarvard architectureThe Harvard architecture is a computer architecture with physically separate storage and signal pathways for instructions and data. The term originated from the Harvard Mark I relay-based computer, which stored instructions on punched tape and data in electro-mechanical counters...
vs von Neumann architectureVon Neumann architectureThe term Von Neumann architecture, aka the Von Neumann model, derives from a computer architecture proposal by the mathematician and early computer scientist John von Neumann and others, dated June 30, 1945, entitled First Draft of a Report on the EDVAC... - Cellular architectureCellular architectureA cellular architecture is a type of computer architecture prominent in parallel computing. Cellular architectures are relatively new, with IBM's Cell microprocessor being the first one to reach the market...
The quantum computer architecture holds the most promise to revolutionize computing.
Sub-definitions
Some practitioners of computer architecture at companies such as Intel and AMD use more fine distinctions:- Macroarchitecture — architectural layers that are more abstract than microarchitecture, e.g. ISA
- Instruction Set Architecture (ISA) — as defined above minus
- Assembly ISA — a smart assembler may convert an abstract assembly language common to a group of machines into slightly different machine language for different implementations
- Programmer Visible Macroarchitecture — higher level language tools such as compilerCompilerA compiler is a computer program that transforms source code written in a programming language into another computer language...
s may define a consistent interface or contract to programmers using them, abstracting differences between underlying ISA, UISA, and microarchitectures. E.g. the CC (programming language)C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
, C++C++C++ is a statically typed, free-form, multi-paradigm, compiled, general-purpose programming language. It is regarded as an intermediate-level language, as it comprises a combination of both high-level and low-level language features. It was developed by Bjarne Stroustrup starting in 1979 at Bell...
, or JavaJava (programming language)Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
standards define different Programmer Visible Macroarchitecture — although in practice the C microarchitecture for a particular computer includes - UISA (Microcode Instruction Set Architecture) — a family of machines with different hardware level microarchitectures may share a common microcode architecture, and hence a UISA.
- Pin Architecture — the set of functions that a microprocessorMicroprocessorA microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
is expected to provide, from the point of view of a hardware platform. E.g. the x86 A20M, FERR/IGNNE or FLUSH pins, and the messages that the processor is expected to emit after completing a cache invalidation so that external caches can be invalidated. Pin architecture functions are more flexible than ISA functions - external hardware can adapt to changing encodings, or changing from a pin to a message - but the functions are expected to be provided in successive implementations even if the manner of encoding them changes.
Computer architecture: the definition
The coordination of abstract levels of a processor under changing forces, involving design, measurement and evaluation. It also includes the overall fundamental working principle of the internal logical structure of a computer system.It can also be defined as the design of the task-performing part of computers, i.e. how various gates and transistors are interconnected and are caused to function per the instructions given by an assembly language programmer.
Instruction set architecture
- The ISA is the interface between the software and hardware.
- It is the set of instructions that bridges the gap between high level languages and the hardware.
- For a processor to understand a command, it should be in binary and not in High Level Language. The ISA encodes these values.
- The ISA also defines the items in the computer that are available to a programmer. For example, it defines data types, registers, addressing modes, memory organization etc.
- Register are high Addressing modes are the ways in which the instructions locate their operands.
Memory organization defines how instructions interact with the memory.
Computer organization
Computer organization helps optimize performance-based products. For example, software engineers need to know the processing ability of processors. They may need to optimize software in order to gain the most performance at the least expense. This can require quite detailed analysis of the computer organization. For example, in a multimedia decoder, the designers might need to arrange for most data to be processed in the fastest data path and the various components are assumed to be in place and task is to investigate the organisational structure to verify the computer parts operates.Computer organization also helps plan the selection of a processor for a particular project. Multimedia projects may need very rapid data access, while supervisory software may need fast interrupts.
Sometimes certain tasks need additional components as well. For example, a computer capable of virtualization needs virtual memory
Virtual memory
In computing, virtual memory is a memory management technique developed for multitasking kernels. This technique virtualizes a computer architecture's various forms of computer data storage , allowing a program to be designed as though there is only one kind of memory, "virtual" memory, which...
hardware so that the memory of different simulated computers can be kept separated.
The computer organization and features also affect the power consumption and the cost
of the processor.
Design goals
The exact form of a computer system depends on the constraints and goals for which it was optimized. Computer architectures usually trade off standards, cost, memory capacity, latency and throughput. Sometimes other considerations, such as features, size, weight, reliability, expandability and power consumption are factors as well.The most common scheme carefully chooses the bottleneck that most reduces the computer's speed. Ideally, the cost is allocated proportionally to assure that the data rate is nearly the same for all parts of the computer, with the most costly part being the slowest. This is how skillful commercial integrators optimize personal computer
Personal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...
s.
Performance
Modern computer architectural performance is often described as MIPS per MHz (millions of instructions per second per millions of cycles per second of clock speedClock rate
The clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
). This metric explicitly measures the efficiency of the architecture at any clock speed. Since a faster clock can make a faster computer, this is a useful, widely applicable measurement. Historic complex instruction set computers had MIPs/MHz as low as 0.1 (See instructions per second
Instructions per second
Instructions per second is a measure of a computer's processor speed. Many reported IPS values have represented "peak" execution rates on artificial instruction sequences with few branches, whereas realistic workloads typically lead to significantly lower IPS values...
). Simple modern processors easily reach near 1. Superscalar
Superscalar
A superscalar CPU architecture implements a form of parallelism called instruction level parallelism within a single processor. It therefore allows faster CPU throughput than would otherwise be possible at a given clock rate...
processors may reach three to five by executing several instructions per clock cycle. Multicore and vector processing CPUs can multiply this further by acting on a lot of data per instruction, and have several CPUs executing in parallel.
Counting machine language instructions would be misleading because they can do varying amounts of work in different ISAs. The "instruction" in the standard measurements is not a count of the ISA's actual machine language instructions, but a historical unit of measurement, usually based on the speed of the VAX
VAX
VAX was an instruction set architecture developed by Digital Equipment Corporation in the mid-1970s. A 32-bit complex instruction set computer ISA, it was designed to extend or replace DEC's various Programmed Data Processor ISAs...
computer architecture.
Historically, many people measured the speed by the clock rate (usually in MHz or GHz). This refers to the cycles per second of the main clock of the CPU. However, this metric is somewhat misleading, as a machine with a higher clock rate may not necessarily have higher performance. As a result manufacturers have moved away from clock speed as a measure of performance.
Computer performance can also be measured with the amount of cache a processor has. If the speed, MHz or GHz, were to be a car then the cache is like the gas tank. No matter how fast the car goes, it will still need to get gas. The higher the speed, and the greater the cache, the faster a processor runs.
Other factors influence speed, such as the mix of functional units, bus
Computer bus
In computer architecture, a bus is a subsystem that transfers data between components inside a computer, or between computers.Early computer buses were literally parallel electrical wires with multiple connections, but the term is now used for any physical arrangement that provides the same...
speeds, available memory, and the type and order of instructions in the programs being run.
In a typical home computer, the simplest, most reliable way to speed performance is usually to add random access memory (RAM). More RAM increases the likelihood that needed data or a program will be in RAM. So, the system is less likely to need to move memory data from the disk. The disk is often ten thousand times slower than RAM because it has mechanical parts that must move to access its data.
There are two main types of speed, latency and throughput. Latency is the time between the start of a process and its completion. Throughput is the amount of work done per unit time. Interrupt latency
Interrupt latency
In real-time operating systems, interrupt latency is the time between the generation of an interrupt by a device and the servicing of the device which generated the interrupt. For many operating systems, devices are serviced as soon as the device's interrupt handler is executed...
is the guaranteed maximum response time of the system to an electronic event (e.g. when the disk drive finishes moving some data).
Performance is affected by a very wide range of design choices — for example, pipelining a processor usually makes latency worse (slower) but makes throughput better. Computers that control machinery usually need low interrupt latencies. These computers operate in a real-time
Real-time computing
In computer science, real-time computing , or reactive computing, is the study of hardware and software systems that are subject to a "real-time constraint"— e.g. operational deadlines from event to system response. Real-time programs must guarantee response within strict time constraints...
environment and fail if an operation is not completed in a specified amount of time. For example, computer-controlled anti-lock brakes must begin braking within a predictable, short time after the brake pedal is sensed.
The performance of a computer can be measured using other metrics, depending upon its application domain. A system may be CPU bound
CPU bound
In computer science, CPU bound is when the time for a computer to complete a task is determined principally by the speed of the central processor: processor utilization is high, perhaps at 100% usage for many seconds or minutes...
(as in numerical calculation), I/O bound (as in a webserving application) or memory bound (as in video editing). Power consumption has become important in servers and portable devices like laptops.
Benchmark
Benchmark (computing)
In computing, a benchmark is the act of running a computer program, a set of programs, or other operations, in order to assess the relative performance of an object, normally by running a number of standard tests and trials against it...
ing tries to take all these factors into account by measuring the time a computer takes to run through a series of test programs. Although benchmarking shows strengths, it may not help one to choose a computer. Often the measured machines split on different measures. For example, one system might handle scientific applications quickly, while another might play popular video games more smoothly. Furthermore, designers have been known to add special features to their products, whether in hardware or software, which permit a specific benchmark to execute quickly but which do not offer similar advantages to other, more general tasks.
Power consumption
Power consumption is another design criterion that factors in the design of modern computers. Power efficiency can often be traded for performance or cost benefits. the typical measurement in this case is MIPS/W (millions of instructions per watt).With the increasing power density of modern circuits as the number of transistors per chip scales (Moore's law
Moore's Law
Moore's law describes a long-term trend in the history of computing hardware: the number of transistors that can be placed inexpensively on an integrated circuit doubles approximately every two years....
), power efficiency has increased in importance. Recent processor designs such as the Intel Core 2
Intel Core 2
Core 2 is a brand encompassing a range of Intel's consumer 64-bit x86-64 single-, dual-, and quad-core microprocessors based on the Core microarchitecture. The single- and dual-core models are single-die, whereas the quad-core models comprise two dies, each containing two cores, packaged in a...
put more emphasis on increasing power efficiency. Also, in the world of embedded computing, power efficiency has long been and remains an important goal next to throughput and latency.
See also
- Computer hardwareComputer hardwarePersonal computer hardware are component devices which are typically installed into or peripheral to a computer case to create a personal computer upon which system software is installed including a firmware interface such as a BIOS and an operating system which supports application software that...
- CPU designCPU designCPU design is the design engineering task of creating a central processing unit , a component of computer hardware. It is a subfield of electronics engineering and computer engineering.- Overview :CPU design focuses on these areas:...
- Orthogonal instruction setOrthogonal instruction setOrthogonal instruction set is a term used in computer engineering. A computer's instruction set is said to be orthogonal if any instruction can use data of any type via any addressing mode...
- Software architectureSoftware architectureThe software architecture of a system is the set of structures needed to reason about the system, which comprise software elements, relations among them, and properties of both...
- von Neumann architectureVon Neumann architectureThe term Von Neumann architecture, aka the Von Neumann model, derives from a computer architecture proposal by the mathematician and early computer scientist John von Neumann and others, dated June 30, 1945, entitled First Draft of a Report on the EDVAC...
- Influence of the IBM PC on the personal computer market
- Comparison of CPU architecturesComparison of CPU architectures- Bits :Computer architectures are often described as n-bit architectures. Today n is often 8, 16, 32, or 64, but other sizes have been used. This is actually a strong simplification. A computer architecture often has a few more or less "natural" datasizes in the instruction set, but the hardware...
External links
- ISCA: Proceedings of the International Symposium on Computer Architecture
- Micro: IEEE/ACM International Symposium on Microarchitecture
- HPCA: International Symposium on High Performance Computer Architecture
- ASPLOS: International Conference on Architectural Support for Programming Languages and Operating Systems
- ACM Transactions on Computer Systems
- ACM Transactions on Architecture and Code Optimization
- IEEE Computer Society
- http://www.cs.wisc.edu/~arch/www
- http://www.codeproject.com/useritems/System_Design.asp - This approach allows beginners to easily break and design complex software systems.
- The von Neumann Architecture of Computer Systems
- A study guide for computer architects