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Encyclopedia > Reduced Instruction Set Computer

The reduced instruction set computer, or RISC, is a CPU design philosophy that favors an instruction set reduced both in size and complexity of addressing modes, in order to enable easier implementation, greater instruction level parallelism, and more efficient compilers. As of 2007, common RISC microprocessors families include the DEC Alpha, ARC, ARM, AVR, MIPS, PA-RISC, Power Architecture (including PowerPC), and SPARC. CPU design is the hardware design of a central processing unit. ... It has been suggested that some sections of this article be split into a new article entitled instruction set architecture. ... Addressing modes, a concept from computer science, are an aspect of the instruction set architecture in most central processing unit (CPU) designs. ... Instruction-level parallelism (ILP) is a measure of how many of the operations in a computer program can be dealt with at once. ... A diagram of the operation of a typical multi-language, multi-target compiler. ... 2007 is a common year starting on Monday of the Gregorian calendar. ... DEC Alpha AXP 21064 Microprocessor die photo Package for DEC Alpha AXP 21064 Microprocessor Alpha AXP 21064 bare die mounted on a business card with some statistics The DEC Alpha, also known as the Alpha AXP, is a 64-bit RISC microprocessor originally developed and fabricated by Digital Equipment Corp... ARC International plc is a company that designs computer processors. ... The ARM architecture (previously, the Advanced RISC Machine, and prior to that Acorn RISC Machine) is a 32-bit RISC processor architecture developed by ARM Limited that is widely used in a number of embedded designs. ... The AVR®s are a family of RISC microcontrollers from Atmel. ... A MIPS R4400 microprocessor made by Toshiba. ... PA-RISC is a microprocessor architecture developed by Hewlett-Packards Systems & VLSI Technology Operation. ... The Power Architecture logo Power Architecture is a broad term to describe similar instruction sets for RISC microprocessors developed and manufactured by such companies as IBM, Freescale, AMCC, Tundra and P.A. Semi. ... PowerPC is a RISC microprocessor architecture created by the 1991 Apple–IBM–Motorola alliance, known as AIM. Originally intended for personal computers, PowerPC CPUs have since become popular embedded and high-performance processors as well. ... Sun UltraSPARC II Microprocessor Sun UltraSPARC T1 (Niagara 8 Core) SPARC (Scalable Processor Architecture) is a RISC microprocessor instruction set architecture originally designed in 1985 by Sun Microsystems. ...


The idea was originally inspired by the discovery that many of the features that were included in traditional CPU designs to facilitate coding were being ignored by the programs that were running on them. Also these more complex features took several processor cycles to be performed. Additionally, the performance gap between the processor and main memory was increasing. This led to a number of techniques to streamline processing within the CPU, while at the same time attempting to reduce the total number of memory accesses. Die of an Intel 80486DX2 microprocessor (actual size: 12×6. ... A computer program is a collection of instructions that describe a task, or set of tasks, to be carried out by a computer. ...

Contents

Pre-RISC design philosophy

For more details on this topic, see CPU design.

In the early days of the computer industry, compiler technology did not exist at all. Programming was done in either machine code or assembly language. To make programming easier, computer architects created more and more complex instructions, which were direct representations of high level functions of high level programming languages. The attitude at the time was that hardware design was easier than compiler design, so the complexity went into the hardware. CPU design is the hardware design of a central processing unit. ... A diagram of the operation of a typical multi-language, multi-target compiler. ... Machine code or machine language is a system of instructions and data directly understandable by a computers central processing unit. ... See the terminology section, below, regarding inconsistent use of the terms assembly and assembler. ...


Another force that encouraged complexity was the lack of large memory. Since memory was small, it was advantageous for the density of information held in computer programs to be very high. When every byte of memory was precious, for example one's entire system only had a few kilobytes of storage, it moved the industry to such features as highly encoded instructions, instructions which could be variable sized, instructions which did multiple operations and instructions which did both data movement and data calculation. At that time, such instruction packing issues were of higher priority than the ease of decoding such instructions. In computer science a byte (pronounced bite) is a unit of measurement of information storage, most often consisting of eight bits. ...


Another reason to keep the density of information high was that memory was not only small, but also quite slow, usually implemented using ferrite core memory technology. By having dense information packing, one could decrease the frequency with which one had to access this slow resource. A 16×16 cm area core memory plane of 128×128 bits, i. ...


CPUs had few registers for two reasons:

  • bits in internal CPU registers are always more expensive than bits in external memory. The available level of silicon integration of the day meant large register sets would have been burdensome to the chip area or board areas available.
  • Having a large number of registers would have required a large number of instruction bits (using precious RAM) to be used as register specifiers.

For the above reasons, CPU designers tried to make instructions that would do as much work as possible. This led to one instruction that would do all of the work in a single instruction: load up the two numbers to be added, add them, and then store the result back directly to memory. Another version would read the two numbers from memory, but store the result in a register. Another version would read one from memory and the other from a register and store to memory again. And so on. This processor design philosophy eventually became known as Complex Instruction Set Computer (CISC) once the RISC philosophy came onto the scene. A complex instruction set computer (CISC) is a microprocessor instruction set architecture (ISA) in which each instruction can execute several low-level operations, such as a load from memory, an arithmetic operation, and a memory store, all in a single instruction. ...


The general goal at the time was to provide every possible addressing mode for every instruction, a principle known as "orthogonality." This led to some complexity on the CPU, but in theory each possible command could be tuned individually, making the design faster than if the programmer used simpler commands. Addressing modes, a concept from computer science, are an aspect of the instruction set architecture in most central processing unit (CPU) designs. ...


The ultimate expression of this sort of design can be seen at two ends of the power spectrum, the 6502 at one end, and the VAX at the other. The $25 single-chip 1 MHz 6502 had only a single general-purpose register, but its simplistic single-cycle memory interface allowed byte-wide operations to perform almost on par with significantly higher clocked designs, such as a 4 MHz Zilog Z80 using equally slow memory chips (i.e. approx. 300ns). The VAX was a minicomputer whose initial implementation required 3 racks of equipment for a single cpu, and was notable for the amazing variety of memory access styles it supported, and the fact that every one of them was available for every instruction. The MOS Technology 6502 is an 8-bit microprocessor that was designed by Chuck Peddle for MOS Technology in 1975. ... VAX is a 32-bit computing architecture that supports an orthogonal instruction set (machine language) and virtual addressing (i. ... One of the first Z80 microprocessors manufactured; the date stamp is from June 1976. ... Minicomputer (colloquially, mini) is a largely obsolete term for a class of multi-user computers which make up the middle range of the computing spectrum, in between the largest multi-user systems (traditionally, mainframe computers) and the smallest single-user systems (microcomputers or personal computers). ... Addressing modes, a concept from computer science, are an aspect of the instruction set architecture in most central processing unit (CPU) designs. ...


RISC design philosophy

In the late 1970s researchers at IBM (and similar projects elsewhere) demonstrated that the majority of these "orthogonal" addressing modes were ignored by most programs. This was a side effect of the increasing use of compilers to generate the programs, as opposed to writing them in assembly language. The compilers in use at the time only had a limited ability to take advantage of the features provided by CISC CPUs; this was largely a result of the difficulty of writing a compiler. The market was clearly moving to even wider use of compilers, diluting the usefulness of these orthogonal modes even more. IBM redirects here. ... Addressing modes, a concept from computer science, are an aspect of the instruction set architecture in most central processing unit (CPU) designs. ... A diagram of the operation of a typical multi-language, multi-target compiler. ... See the terminology section, below, regarding inconsistent use of the terms assembly and assembler. ... A complex instruction set computer (CISC) is a microprocessor instruction set architecture (ISA) in which each instruction can execute several low-level operations, such as a load from memory, an arithmetic operation, and a memory store, all in a single instruction. ...


Another discovery was that these operations were rarely used; in fact, they tended to be slower than a number of smaller operations doing the same thing. This seeming paradox was a side effect of the time spent designing the CPUs: designers simply did not have time to tune every possible instruction, and instead only tuned the ones used most often. One famous example of this was the VAX's INDEX instruction, which ran slower than a loop implementing the same code.[1] Look up paradox in Wiktionary, the free dictionary. ... VAX is a 32-bit computing architecture that supports an orthogonal instruction set (machine language) and virtual addressing (i. ...


At about the same time CPUs started to run even faster than the memory they talked to. Even in the late 1970s it was apparent that this disparity was going to continue to grow for at least the next decade, by which time the CPU would be tens to hundreds of times faster than the memory. It became apparent that more registers (and later caches) would be needed to support these higher operating frequencies. These additional registers and cache memories would require sizeable chip or board areas that could be made available if the complexity of the CPU was reduced. In computer architecture, a processor register is a small amount of very fast computer memory used to speed the execution of computer programs by providing quick access to commonly used values—typically, the values being in the midst of a calculation at a given point in time. ... Look up cache in Wiktionary, the free dictionary. ...


Yet another part of RISC design came from practical measurements on real-world programs. Andrew Tanenbaum summed up many of these, demonstrating that most processors were vastly overdesigned. For instance, he showed that 98% of all the constants in a program would fit in 13 bits, yet almost every CPU design dedicated some multiple of 8 bits to store them, typically 8, 16 or 32, one entire word. Taking this fact into account suggests that a machine should allow for constants to be stored in unused bits of the instruction itself, decreasing the number of memory accesses. Instead of loading up numbers from memory or registers, they would be "right there" when the CPU needed them, and therefore much faster. However this required the operation itself to be very small, otherwise there would not be enough room left over in a 32-bit instruction to hold reasonably sized constants. Andrew S. Tanenbaum Dr. Andrew Stuart Andy Tanenbaum (sometimes called ast)[1] (born 1944) is a professor of computer science at the Vrije Universiteit, Amsterdam in the Netherlands. ... This article is about the unit of information. ... In computing, word is a term for the natural unit of data used by a particular computer design. ...


Since real-world programs spent most of their time executing very simple operations, some researchers decided to focus on making those common operations as simple and as fast as possible. Since the clock rate of the CPU is limited by the time it takes to execute the slowest instruction, speeding up that instruction -- perhaps by reducing the number of addressing modes it supports -- also speeds up the execution of every other instruction. The goal of RISC was to make instructions so simple, each one could be executed in a single clock cycle[1]. The focus on "reduced instructions" led to the resulting machine being called a "reduced instruction set computer" (RISC). It has been suggested that this article or section be merged into Clock signal. ...


The main difference between RISC and CISC is that RISC architecture instructions either (a) perform operations on the registers or (b) load and store the data to and from them. Many CISC instructions, on the other hand, combine these steps. To clarify this difference, many researchers use the term load-store to refer to RISC.


Over time the older design technique became known as Complex Instruction Set Computer, or CISC, although this was largely to give it a different name for comparison purposes. A complex instruction set computer (CISC) is a microprocessor instruction set architecture (ISA) in which each instruction can execute several low-level operations, such as a load from memory, an arithmetic operation, and a memory store, all in a single instruction. ...


Code was implemented as a series of these simple instructions, instead of a single complex instruction that had the same result. This had the side effect of leaving more room in the instruction to carry data with it, meaning that there was less need to use registers or memory. At the same time the memory interface was considerably simpler, allowing it to be tuned.


However RISC also had its drawbacks. Since a series of instructions is needed to complete even simple tasks, the total number of instructions read from memory is larger, and therefore takes longer. At the time it was not clear whether or not there would be a net gain in performance due to this limitation, and there was an almost continual battle in the press and design world about the RISC concepts.


Other solutions

While the RISC philosophy was coming into its own, new ideas about how to dramatically increase performance of the CPUs were starting to develop.


In the early 1980s it was thought that existing design was reaching theoretical limits. Future improvements in speed would be primarily through improved semiconductor "process", that is, smaller features (transistors and wires) on the chip. The complexity of the chip would remain largely the same, but the smaller size would allow it to run at higher clock rates. A considerable amount of effort was put into designing chips for parallel computing, with built-in communications links. Instead of making faster chips, a large number of chips would be used, dividing up problems among them. However, history has shown that the original fears were not valid and there were a number of ideas that dramatically improved performance in the late 1980s. A semiconductor is a fuckin solid whose electrical conductivity is in between that of a metal and that of an insulator, and can be controlled over a wide range, either permanently or dynamically. ... Photo of transistor types (tape measure marked in centimeters) Transistor in the SMD form factor The transistor is a solid state semiconductor device used for amplification and switching. ... Parallel computing is the simultaneous execution of the same task (split up and specially adapted) on multiple processors in order to obtain results faster. ...


One idea was to include a pipeline which would break down instructions into steps, and work on one step of several different instructions at the same time. A normal processor might read an instruction, decode it, fetch the memory the instruction asked for, perform the operation, and then write the results back out. The key to pipelining is the observation that the processor can start reading the next instruction as soon as it finishes reading the last, meaning that there are now two instructions being worked on (one is being read, the next is being decoded), and after another cycle there will be three. While no single instruction is completed any faster, the next instruction would complete right after the previous one. The result was a much more efficient utilization of processor resources.


Yet another solution was to use several processing elements inside the processor and run them in parallel. Instead of working on one instruction to add two numbers, these superscalar processors would look at the next instruction in the pipeline and attempt to run it at the same time in an identical unit. However, this can be difficult to do, as many instructions in computing depend on the results of some other instruction. Simple superscalar pipeline. ...


Both of these techniques relied on increasing speed by adding complexity to the basic layout of the CPU, as opposed to the instructions running on them. With chip space being a finite quantity, in order to include these features something else would have to be removed to make room. RISC was tailor-made to take advantage of these techniques, because the core logic of a RISC CPU was considerably simpler than in CISC designs. Although the first RISC designs had marginal performance, they were able to quickly add these new design features and by the late 1980s they were significantly outperforming their CISC counterparts. In time this would be addressed as process improved to the point where all of this could be added to a CISC design and still fit on a single chip, but this took most of the late-80s and early 90s.


The long and short of it is that for any given level of general performance, a RISC chip will typically have many fewer transistors dedicated to the core logic. This allows the designers considerable flexibility; they can, for instance: Assorted discrete transistors A transistor is a semiconductor device, commonly used as an amplifier or an electrically controlled switch. ...

  • increase the size of the register set
  • implement measures to increase internal parallelism
  • increase the size of caches
  • add other functionality, like I/O and timers for microcontrollers
  • add vector (SIMD) processors like AltiVec and Streaming SIMD Extensions (SSE)
  • build the chips on older fabrication lines, which would otherwise go unused
  • do nothing; offer the chip for battery-constrained or size-limited applications

Features which are generally found in RISC designs are: Diagram of a CPU memory cache A CPU cache is a cache used by the central processing unit of a computer to reduce the average time to access memory. ... -1... AltiVec is a floating point and integer SIMD instruction set designed and owned by Apple Computer, IBM and Motorola (the AIM alliance), and implemented on versions of the PowerPC including Motorolas G4 and IBMs G5 processors. ... SSE (Streaming SIMD Extensions, originally called ISSE, Internet Streaming SIMD Extensions) is a SIMD (Single Instruction, Multiple Data) instruction set designed by Intel and introduced in 1999 in their Pentium III series processors as a reply to AMDs 3DNow! (which had debuted a year earlier). ... Symbols representing a single Cell (top) and Battery (bottom), used in circuit diagrams. ...

  • uniform instruction encoding (for example the op-code is always in the same bit position in each instruction, which is always one word long), which allows faster decoding;
  • a homogeneous register set, allowing any register to be used in any context and simplifying compiler design (although there are almost always separate integer and floating point register files);
  • simple addressing modes (complex addressing modes are replaced by sequences of simple arithmetic instructions);
  • few data types supported in hardware (for example, some CISC machines had instructions for dealing with byte strings. Others had support for polynomials and complex numbers. Such instructions are unlikely to be found on a RISC machine).

RISC designs are also more likely to feature a Harvard memory model, where the instruction stream and the data stream are conceptually separated; this means that modifying the addresses where code is held might not have any effect on the instructions executed by the processor (because the CPU has a separate instruction and data cache), at least until a special synchronization instruction is issued. On the upside, this allows both caches to be accessed simultaneously, which can often improve performance. The integers are commonly denoted by the above symbol. ... A floating-point number is a digital representation for a number in a certain subset of the rational numbers, and is often used to approximate an arbitrary real number on a computer. ... Addressing modes, a concept from computer science, are an aspect of the instruction set architecture in most central processing unit (CPU) designs. ... In computer science a byte (pronounced bite) is a unit of measurement of information storage, most often consisting of eight bits. ... In computer programming and formal language theory, (and other branches of mathematics), a string is an ordered sequence of symbols. ... In mathematics, a complex number is a number of the form where a and b are real numbers, and i is the imaginary unit, with the property i 2 = −1. ... The term Harvard architecture originally referred to computer architectures that used physically separate storage and signal pathways for their instructions and data (in contrast to the von Neumann architecture). ... Look up cache in Wiktionary, the free dictionary. ...


Many of these early RISC designs also shared the characteristic of having a branch delay slot. A branch delay slot is an instruction space immediately following a jump or branch. The instruction in this space is executed whether or not the branch is taken (in other words the effect of the branch is delayed). This instruction keeps the ALU of the CPU busy for the extra time normally needed to perform a branch. Nowadays the branch delay slot is considered an unfortunate side effect of a particular strategy for implementing some RISC designs, and modern RISC designs generally do away with it (such as PowerPC, more recent versions of SPARC, and MIPS). In computer architecture, a branch delay instruction is an instruction immediately following a conditional branch instruction which is executed whether or not the branch is taken. ... ALU redirects here. ... PowerPC is a RISC microprocessor architecture created by the 1991 Apple–IBM–Motorola alliance, known as AIM. Originally intended for personal computers, PowerPC CPUs have since become popular embedded and high-performance processors as well. ...


Early RISC

The first system that would today be known as RISC was not at the time; it was the CDC 6600 supercomputer, designed in 1964 by Jim Thornton and Seymour Cray. Thornton and Cray designed it as a number-crunching CPU (with 74 opcodes, compared with a 8086's 400) plus 12 simple computers called "peripheral processors" to handle I/O (most of the operating system was in one of these). The CDC 6600 had a load-store architecture with only two addressing modes. There were eleven pipelined functional units for arithmetic and logic, plus five load units and two store units (the memory had multiple banks so all load-store units could operate at the same time). The basic clock cycle/instruction issue rate was 10 times faster than the memory access time. The CDC 6600 was a mainframe computer from Control Data Corporation, first manufactured in 1965. ... A supercomputer is a computer that led the world (or was close to doing so) in terms of processing capacity, particularly speed of calculation, at the time of its introduction. ... Seymour Roger Cray (September 28, 1925 â€“ October 5, 1996) was a U.S. electrical engineer and supercomputer architect who founded the company Cray Research. ... The intels 8086 was the first one launched in 1978. ... Addressing modes, a concept from computer science, are an aspect of the instruction set architecture in most central processing unit (CPU) designs. ...


Another early load-store machine was the Data General Nova minicomputer, designed in 1968. Data General SuperNova The Data General Nova was a popular 16-bit minicomputer built by the United States company Data General starting in 1969. ...


The earliest attempt to make a chip-based RISC CPU was a project at IBM which started in 1975. Named after the building where the project ran, the work led to the IBM 801 CPU family which was used widely inside IBM hardware. The 801 was eventually produced in a single-chip form as the ROMP in 1981, which stood for Research (Office Products Division) Mini Processor. As the name implies, this CPU was designed for "mini" tasks, and when IBM released the IBM RT-PC based on the design in 1986, the performance was not acceptable. Nevertheless the 801 inspired several research projects, including new ones at IBM that would eventually lead to their POWER system. International Business Machines Corporation (IBM, or colloquially, Big Blue) (NYSE: IBM) (incorporated June 15, 1911, in operation since 1888) is headquartered in Armonk, New York, USA. The company manufactures and sells computer hardware, software, and services. ... The 801 was a RISC microprocessor architecture designed by IBM in the 1970s, and used in various roles in IBM until the 1980s. ... RISC Technology Personal Computer. ... POWER is a RISC instruction set architecture designed by IBM. The name is a acronym for Performance Optimization With Enhanced RISC. POWER is also the name of a series of microprocessors that implements the instruction set architecture. ...


The most public RISC designs, however, were the results of university research programs run with funding from the DARPA VLSI Program. The VLSI Program, practically unknown today, led to a huge number of advances in chip design, fabrication, and even computer graphics. The Defense Advanced Research Projects Agency (DARPA) is an agency of the United States Department of Defense responsible for the development of new technology for use by the military. ... Very-large-scale integration (VLSI) of systems of transistor-based circuits into integrated circuits on a single chip first occurred in the 1980s as part of the semiconductor and communication technologies that were being developed. ...


UC Berkeley's RISC project started in 1980 under the direction of David Patterson, based on gaining performance through the use of pipelining and an aggressive use of registers known as register windows. In a normal CPU one has a small number of registers, and a program can use any register at any time. In a CPU with register windows, there are a huge number of registers, e.g. 128, but programs can only use a small number of them, e.g. 8, at any one time. A program that limits itself to 8 registers per procedure can make very fast procedure calls: The call simply moves the window "down" by 8, to the set of 8 registers used by that procedure, and the return moves the window back. (On a normal CPU, most calls must save at least a few registers' values to the stack in order to use those registers as working space, and restore their values on return.) The University of California, Berkeley (also known as Cal, UC Berkeley, UCB, or simply Berkeley) is a prestigious, public, coeducational university situated in the foothills of Berkeley, California to the east of San Francisco Bay, overlooking the Golden Gate and its bridge. ... Berkeley RISC was one of two seminal research projects into RISC-based microprocessor design taking place under ARPAs VLSI project. ... David A. Patterson has been Professor of Computer Science at the University of California, Berkeley since 1977. ... In computer engineering, the use of register windows is a technique to improve the performance of a particularly common operation, the procedure call. ... In computer engineering, the use of register windows is a technique to improve the performance of a particularly common operation, the procedure call. ...


The RISC project delivered the RISC-I processor in 1982. Consisting of only 44,420 transistors (compared with averages of about 100,000 in newer CISC designs of the era) RISC-I had only 32 instructions, and yet completely outperformed any other single-chip design. They followed this up with the 40,760 transistor, 39 instruction RISC-II in 1983, which ran over three times as fast as RISC-I.


At about the same time, John L. Hennessy started a similar project called MIPS at Stanford University in 1981. MIPS focused almost entirely on the pipeline, making sure it could be run as "full" as possible. Although pipelining was already in use in other designs, several features of the MIPS chip made its pipeline far faster. The most important, and perhaps annoying, of these features was the demand that all instructions be able to complete in one cycle. This demand allowed the pipeline to be run at much higher speeds (there was no need for induced delays) and is responsible for much of the processor's speed. However, it also had the negative side effect of eliminating many potentially useful instructions, like a multiply or a divide. John LeRoy Hennessy, the founder of MIPS Computer Systems Inc. ... A MIPS R4400 microprocessor made by Toshiba. ... Leland Stanford Junior University, commonly known as Stanford University (or simply Stanford), is a private university located approximately 37 miles (60 kilometers) southeast of San Francisco and approximately 20 miles northwest of San José in Stanford, California. ...


In the early years, the RISC efforts were well known, but largely confined to the university labs that had created them. The Berkeley effort became so well known that it eventually became the name for the entire concept. Many in the computer industry criticized that the performance benefits were unlikely to translate into real-world settings due to the decreased memory efficiency of multiple instructions, and that that was the reason no one was using them. But starting in 1986, all of the RISC research projects started delivering products. In fact, almost all modern RISC processors are direct copies of the RISC-II design.


Later RISC

Berkeley's research was not directly commercialized, but the RISC-II design was used by Sun Microsystems to develop the SPARC, by Pyramid Technology to develop their line of mid-range multi-processor machines, and by almost every other company a few years later. It was Sun's use of a RISC chip in their new machines that demonstrated that RISC's benefits were real, and their machines quickly outpaced the competition and essentially took over the entire workstation market. Sun Microsystems, Inc. ... Sun UltraSPARC II Microprocessor Sun UltraSPARC T1 (Niagara 8 Core) SPARC (Scalable Processor Architecture) is a RISC microprocessor instruction set architecture originally designed in 1985 by Sun Microsystems. ... Pyramid Technology was a computer company that produced a number of RISC-based minicomputers at the upper-end of the performance range. ... Sun SPARCstation 1+, 25 MHz RISC processor from early 1990s A workstation, such as a Unix workstation, RISC workstation or engineering workstation, is a high-end desktop or deskside microcomputer designed for technical applications. ...


John Hennessy left Stanford (temporarily) to commercialize the MIPS design, starting the company known as MIPS Computer Systems. Their first design was a second-generation MIPS chip known as the R2000. MIPS designs went on to become one of the most used RISC chips when they were included in the PlayStation and Nintendo 64 game consoles. Today they are one of the most common embedded processors in use for high-end applications. MIPS Technologies, formerly MIPS Computer Systems, is most widely known for developing the MIPS architecture, a series of pioneering RISC CPUs. ... MIPS, for Microprocessor without interlocked pipeline stages, is a RISC microprocessor architecture developed by MIPS Computer Systems Inc. ... The Sony PlayStation ) is a video game console of the 32/64-bit era, first produced by Sony Computer Entertainment in the mid-1990s. ... The Nintendo 64 ), often abbreviated as N64, was Nintendos third home video game console for the international market. ... The Nintendo GameCube is an example of a popular video game console. ... This page is a candidate for speedy deletion, because: it is patent nonsense. ...


IBM learned from the RT-PC failure and went on to design the RS/6000 based on their new POWER architecture. They then moved their existing AS/400 systems to POWER chips, and found much to their surprise that even the very complex instruction set ran considerably faster. POWER would also find itself moving "down" in scale to produce the PowerPC design, which eliminated many of the "IBM only" instructions and created a single-chip implementation. Today the PowerPC is one of the most commonly used CPUs for automotive applications (some cars have over 10 of them inside). It was also the CPU used in most Apple Macintosh machines sold until 2006. Starting in February 2006, Apple switched their PowerPC products to Intel x86 processors. i5 Model 570 (2006) The Application System/400 (also known as AS/400, iSeries (since 2000) and System i5 (since 2006)) is a type of minicomputer produced by IBM. It was first produced in 1988 and, as of 2006, is still in production. ... PowerPC is a RISC microprocessor architecture created by the 1991 Apple–IBM–Motorola alliance, known as AIM. Originally intended for personal computers, PowerPC CPUs have since become popular embedded and high-performance processors as well. ... PowerPC is a RISC microprocessor architecture created by the 1991 Apple–IBM–Motorola alliance, known as AIM. Originally intended for personal computers, PowerPC CPUs have since become popular embedded and high-performance processors as well. ... The first Macintosh computer, introduced in 1984, upgraded to a 512K Fat Mac. The Macintosh or Mac, is a line of personal computers designed, developed, manufactured, and marketed by Apple Computer. ... PowerPC is a RISC microprocessor architecture created by the 1991 Apple–IBM–Motorola alliance, known as AIM. Originally intended for personal computers, PowerPC CPUs have since become popular embedded and high-performance processors as well. ... Intel Corporation (NASDAQ: INTC, SEHK: 4335), founded in 1968 as Integrated Electronics Corporation, is an American multinational corporation that is best known for designing and manufacturing microprocessors and specialized integrated circuits. ... x86 or 80x86 is the generic name of a microprocessor architecture first developed and manufactured by Intel. ...


Almost all other vendors quickly joined. From the UK similar research efforts resulted in the INMOS transputer, the Acorn Archimedes and the Advanced RISC Machine line, which is a huge success today. Companies with existing CISC designs also quickly joined the revolution. Intel released the i860 and i960 by the late 1980s, although they were not very successful. Motorola built a new design called the 88000 in homage to their famed CISC 68000, but it saw almost no use and they eventually abandoned it and joined IBM to produce the PowerPC. AMD released their 29000 which would go on to become the most popular RISC design of the early 1990s. T414B transputer chip The INMOS transputer (the all-lowercase transputer was the official written form) was a pioneering concurrent computing microprocessor design of the 1980s from INMOS, a British semiconductor company based in Bristol (the University of the West of England in Bristol had, for a while, a transputer centre). ... This article or section does not cite its references or sources. ... The entrance to ARMs headquarters in Cherry Hinton, Cambridge ARM (Advanced RISC Machines) Ltd is a microprocessor design company headquartered in England, founded in 1990 by Hermann Hauser. ... Intel Corporation (NASDAQ: INTC, SEHK: 4335), founded in 1968 as Integrated Electronics Corporation, is an American multinational corporation that is best known for designing and manufacturing microprocessors and specialized integrated circuits. ... The Intel i860 (also 80860, and code named N10) was a RISC microprocessor from Intel, first released in 1989. ... Intels i960 (or 80960) was a RISC-based microprocessor design that became popular during the early 1990s as an embedded microcontroller, becoming a best-selling CPU in that field, along with the competing AMD 29000. ... Motorola Inc. ... The 88000 (m88k for short) is a microprocessor design produced by Motorola. ... The Motorola 68000 is a 32-bit CISC microprocessor core designed and marketed by Freescale Semiconductor (formerly Motorola Semiconductor Products Sector). ... Advanced Micro Devices, Inc. ... AMD 29000 Microprocessor The AMD 29000, often simply 29k, was a popular family of RISC-based 32-bit microprocessors and microcontrollers from Advanced Micro Devices. ...


Today the vast majority of all 32-bit CPUs in use are RISC CPUs, and microcontrollers. RISC design techniques offers power in even small sizes, and thus has become dominant for low-power 32-bit CPUs. Embedded systems are by far the largest market for processors: while a family may own one or two PCs, their car(s), cell phones, and other devices may contain a total of dozens of embedded processors. RISC had also completely taken over the market for larger workstations for much of the 90s (until taken back by cheap PC-based solutions). After the release of the Sun SPARCstation the other vendors rushed to compete with RISC based solutions of their own. The high-end server market today is almost completely RISC based. It has been suggested that this article or section be merged with embedded microprocessor. ...


RISC and x86

However, despite many successes,RISC has made few inroads into the desktop PC and commodity server markets, where Intel's x86 platform remains the dominant processor architecture (Intel is facing increased competition from AMD, but even AMD's processors implement the x86 platform, or a 64-bit superset known as x86-64). There are three main reasons for this. One, the very large base of proprietary PC applications are written for x86, whereas no RISC platform has a similar installed base, and this meant PC users were locked into the x86. The second is that, although RISC was indeed able to scale up in performance quite quickly and cheaply, Intel took advantage of its large market by spending vast amounts of money on processor development. Intel could spend many times as much as any RISC manufacturer on improving low level design and manufacturing. The same could not be said about smaller firms like Cyrix and NextGen, but they realized that they could apply pipelined design philosophies and practices to the x86-architecture — either directly as in the 6x86 and MII series, or indirectly (via extra decoding stages) as in Nx586 and AMD K5. Later, more powerful processors such as Intel P6 and AMD K6 had similar RISC-like units that executed a stream of micro-operations generated from decoding stages that split most x86 instructions into several pieces. Today, these principles have been further refined and are used by modern x86 processors such as Intel Core 2 and AMD K8. The first available chip deploying such techniques was the NextGen Nx586, released in 1994 (while the AMD K5 was severely delayed and released in 1995). Intel Corporation (NASDAQ: INTC, SEHK: 4335), founded in 1968 as Integrated Electronics Corporation, is an American multinational corporation that is best known for designing and manufacturing microprocessors and specialized integrated circuits. ... x86 or 80x86 is the generic name of a microprocessor architecture first developed and manufactured by Intel. ... Intel Corporation (NASDAQ: INTC, SEHK: 4335), founded in 1968 as Integrated Electronics Corporation, is an American multinational corporation that is best known for designing and manufacturing microprocessors and specialized integrated circuits. ... Advanced Micro Devices, Inc. ... x86 or 80x86 is the generic name of a microprocessor architecture first developed and manufactured by Intel. ... The AMD64 or x86-64 is a 64-bit processor architecture invented by AMD. It is a superset of the x86 architecture, which it natively supports. ... It has been suggested that closed source be merged into this article or section. ... Cyrix corporate logo Cyrix was a CPU manufacturer that began in 1988 as a specialist supplier of high-performance math co-processors for 286 and 386 systems. ... A NexGen Nx586 processor NexGen was a private semiconductor company that designed x86 PC central processing units until it was purchased by AMD in 1996. ... K5 core diagram AMD 5K86-P90 (SSA/5) AMD K5 PR166 The K5 was AMDs first in-house processor, developed to compete with Intels Pentium microprocessor range. ... The P6 microarchitecture is the sixth generation Intel x86 microprocessor architecture, released in 1995. ... History 1997 saw the arrival of AMDs K6 microprocessor. ... The Core 2 brand refers to a range of Intels mobile and desktop 64-bit dual-/quad-core x86 CPUs with the Core microarchitecture, which evolved from the 32-bit dual-core Yonah mobile processor. ... The AMD K8 generation of CPUs is the successor to the AMD K7 generation of CPUs. ...


As of 2007, the x86 designs (whether Intel's or AMD's) are as fast as (if not faster than) the fastest true RISC single-chip solutions available.[2] Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ...


Cost

Consumers are interested in speed, energy efficiency, cost per chip, and compatibility with existing software rather than the cost of development of new chips.[citation needed] This has led to an interesting chain of events. As the complexity of developing ever more advanced CPUs rises, the cost of both development and fabrication of high-end CPUs has exploded. The cost gains given by RISC are now dwarfed by the high costs of developing any modern CPU. Today, only the biggest chip makers are able to make high performing CPUs. The result is that virtually all RISC platforms with the exception of IBM's Power Architecture have greatly shrunk in scale of development of high performing CPUs (like SPARC and MIPS) or were abandoned (like Alpha and PA-RISC) during the 00s. As of 2007, a RISC chip is (again) the fastest CPU in SPECint and SPECfp, which is IBM's Power6 CPU. The Power Architecture logo Power Architecture is a broad term to describe similar instruction sets for RISC microprocessors developed and manufactured by such companies as IBM, Freescale, AMCC, Tundra and P.A. Semi. ... SPECint is a computer benchmark specification for CPUs integer processing power. ... SPECfp (aka CFP2000) is a computer benchmark designed to test the floating point performance of a computer. ... The POWER6 microprocessor is IBMs follow on to the POWER5. ...


Still, RISC designs have led to a number of successful platforms and architectures, some of the larger ones being:

  • MIPS's MIPS line, found in most SGI computers and the PlayStation, PlayStation 2, Nintendo 64 (discontinued), and PlayStation Portable game consoles.
  • IBM's and Freescale's (formerly Motorola SPS) Power Architecture, used in all of IBM's supercomputers, midrange servers and workstations, in Apple's PowerPC-based Macintosh computers (discontinued), in Nintendo's Gamecube and Wii, Microsoft's Xbox 360 and Sony's PlayStation 3 game consoles, and in many embedded applications like printers and cars.
  • Sun's SPARC and UltraSPARC, found in most of their later machines
  • Hewlett-Packard's PA-RISC, also known as HP/PA (discontinued).
  • DEC Alpha, still used in some of HP's workstation and servers (discontinued).
  • XAP processor used in many wireless chips, e.g. Bluetooth
  • ARMPalm, Inc. originally used the (CISC) Motorola 680x0 processors in its early PDAs, but now uses (RISC) ARM processors in its latest PDAs. Many PocketPC PDAs and smartphones run off the Intel XScale or equivalent CPUs (like the Samsung SC32442), which is an implementation of the ARMv5 processor. Apple Inc. uses the ARM 7TDMI in its iPod products, and Samsung's ARM1176jzf processor in the iPhone. Nintendo uses an ARM7 CPU in the Game Boy Advance and both an ARM7 and ARM9 in the Nintendo DS handheld game systems. The small Korean company Game Park also markets the GP32, which uses the ARM9 CPU. Also, many cell phones from, for example, Nokia are based on ARM designs.
  • Hitachi's SuperH, originally in wide use in the Sega Super 32X, Saturn and Dreamcast, now at the heart of many consumer electronics devices. The SuperH is the base platform for the Mitsubishi - Hitachi joint semiconductor group. The two groups merged in 2002, dropping Mitsubishi's own RISC architecture, the M32R.

A MIPS R4400 microprocessor made by Toshiba. ... Silicon Graphics, Inc. ... The Sony PlayStation ) is a video game console of the 32/64-bit era, first produced by Sony Computer Entertainment in the mid-1990s. ... “PS2” redirects here. ... The Nintendo 64 ), often abbreviated as N64, was Nintendos third home video game console for the international market. ... The PlayStation Portable , officially abbreviated as PSP) is a handheld game console released and currently manufactured by Sony Computer Entertainment. ... Motorola Inc. ... The Power Architecture logo Power Architecture is a broad term to describe similar instruction sets for RISC microprocessors developed and manufactured by such companies as IBM, Freescale, AMCC, Tundra and P.A. Semi. ... The Macintosh 128K, the first Macintosh computer The iMac, a current Mac computer Macintosh is a brand name which covers several lines of personal computers designed, developed, and marketed by Apple Inc. ... Nintendo Company, Limited (任天堂 or ニンテンドー Nintendō; NASDAQ: NTDOY, TYO: 7974 usually referred to as simply Nintendo, or Big N ) is a multinational corporation founded on September 23, 1889[1] in Kyoto, Japan by Fusajiro Yamauchi to produce handmade hanafuda cards. ... The Nintendo GameCube , GCN) is Nintendos fourth home video game console, belonging to the sixth generation era. ... The Wii (pronounced as the pronoun we, IPA: ) is the fifth home video game console released by Nintendo. ... Microsoft Corporation, (NASDAQ: MSFT, HKSE: 4338) is a multinational computer technology corporation with global annual revenue of US$44. ... It has been suggested that Xbox 360 Elite be merged into this article or section. ... Sony Corporation ) is a Japanese multinational corporation and one of the worlds largest media conglomerates with revenue of $66. ... The PlayStation 3 , trademarked PLAYSTATION®3,[3] commonly abbreviated PS3) is the third home video game console produced by Sony Computer Entertainment; successor to the PlayStation 2. ... Sun Microsystems, Inc. ... Sun UltraSPARC II Microprocessor Sun UltraSPARC T1 (Niagara 8 Core) SPARC (Scalable Processor Architecture) is a RISC microprocessor instruction set architecture originally designed in 1985 by Sun Microsystems. ... SPARC (Scalable Processor ARChitecture) is a RISC microprocessor architecture originally designed in 1985 by Sun Microsystems. ... The Hewlett-Packard Company (NYSE: HPQ), commonly known as HP, is a very large, global company headquartered in Palo Alto, California, United States. ... PA-RISC is a microprocessor architecture developed by Hewlett-Packards Systems & VLSI Technology Operation. ... DEC Alpha AXP 21064 Microprocessor die photo Package for DEC Alpha AXP 21064 Microprocessor Alpha AXP 21064 bare die mounted on a business card with some statistics The DEC Alpha, also known as the Alpha AXP, is a 64-bit RISC microprocessor originally developed and fabricated by Digital Equipment Corp... A XAP® processor provides the computation element within an Integrated Circuit that has to process digital data. ... Bluetooth logo This article is about the electronic protocol named after Harald Bluetooth Gormson. ... The ARM architecture (previously, the Advanced RISC Machine, and prior to that Acorn RISC Machine) is a 32-bit RISC processor architecture developed by ARM Limited that is widely used in a number of embedded designs. ... Palm, Inc. ... Apple Inc. ... iPod (fifth generation) in Apple Universal Dock, iPod nano (second generation) and iPod shuffle (second generation) iPod is a brand of portable media players designed and marketed by Apple and launched in 2001. ... The correct title of this article is . ... Nintendo Company, Limited (任天堂 or ニンテンドー Nintendō; NASDAQ: NTDOY, TYO: 7974 usually referred to as simply Nintendo, or Big N ) is a multinational corporation founded on September 23, 1889[1] in Kyoto, Japan by Fusajiro Yamauchi to produce handmade hanafuda cards. ... This article does not cite any references or sources. ... “NDS” redirects here. ... Game Park is a Korean company responsible for creating the GP32 and XGP. GP32 Hardware and Design // Founded in 1996 in Korea, Game Park entered the industry using government money. ... Nokia Corporation (OMX: NOK1V, NYSE: NOK, FWB: NOA3) is an international communications company, focused on the key growth areas of wireline and wireless telecommunications. ... It has been suggested that Hitachi Works be merged into this article or section. ... The SuperHichem (or SH) is brandname of a certain microcontroller and microprocessor architecture. ... Sega Corporation ) is a multinational Japanese video game software and hardware development company, and a former home computer and console manufacturer. ... This article does not cite any references or sources. ... The Sega Saturn ) is a 32-bit video game console, first released on November 22, 1994 in Japan, May 11, 1995 in North America and July 8, 1995 in Europe. ... The Dreamcast , code-named White Belt, Black Belt, Dural, Dricas, Vortex, Katana, Shark and Guppy during development) is Segas final video game console and the successor to the Sega Saturn. ... Mitsubishi Logo The Mitsubishi Group ), Mitsubishi Group of Companies, or Mitsubishi Companies, all refer to a large grouping of independently operated Japanese companies which share the Mitsubishi brand name. ... It has been suggested that Hitachi Works be merged into this article or section. ... Also see: 2002 (number). ... The Renesas M32R is a 32-bit embedded RISC microcontroller originally developed and manufactured by Mitsubishi Electric Corporation, succeeded by a FPGA-implemented MMUed M32R variant named mappi which runs Debian/GNU Linux, and is supported by the GNU Compiler Collection. ...

Alternative term

Over many years, RISC instruction sets have tended to grow in size. Thus, some have started using the term "load-store" to describe RISC processors, since this is the key element of all such designs. Instead of the CPU itself handling many addressing modes, a load-store architecture uses a separate unit dedicated to handling very simple forms of load and store operations. CISC processors are then termed "register-memory" or "memory-memory".


See also

Addressing modes, a concept from computer science, are an aspect of the instruction set architecture in most central processing unit (CPU) designs. ... A complex instruction set computer (CISC) is a microprocessor instruction set architecture (ISA) in which each instruction can execute several low-level operations, such as a load from memory, an arithmetic operation, and a memory store, all in a single instruction. ... A Very Long Instruction Word or VLIW CPU architecture implements a form of instruction level parallelism. ... MISC (Minimal Instruction Set Computer) is a processor architecture with a very small number of basic operations and corresponding opcodes. ... In computer science, ZISC stands for Zero Instruction Set Computer, which refers to a chip technology based on pure pattern matching and absence of (micro-)instructions in the classical sense. ... The OISC is the One Instruction Set Computer, by humorous analogy with RISC (Reduced Instruction Set Computer) and CISC (Complex Instruction Set Computer). ... A microprocessor is a programmable digital electronic component that incorporates the functions of a central processing unit (CPU) on a single semiconducting integrated circuit (IC). ... An instruction set, or instruction set architecture (ISA), describes the aspects of a computer architecture visible to a programmer, including the native datatypes, instructions, registers, addressing modes, memory architecture, interrupt and exception handling, and external I/O (if any). ... A typical vision of a computer architecture as a series of abstraction layers: hardware, firmware, assembler, kernel, operating system and applications (see also Tanenbaum 79). ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... Layout of the IBM Cell die Cell is a microprocessor architecture jointly developed by a Sony, Toshiba, and IBM, an alliance known as STI. The architectural design and first implementation were carried out at the STI Design Center over a four-year period beginning March 2001 on a budget reported...

Notes and references

  1. ^ Patterson, D. A. and Ditzel, D. R. 1980. The case for the reduced instruction set computer. SIGARCH Comput. Archit. News 8, 6 (Oct. 1980), 25-33. DOI= http://doi.acm.org/10.1145/641914.641917
  2. ^ http://www.spec.org/cpu2006/results/

David A. Patterson has been Professor of Computer Science at the University of California, Berkeley since 1977. ...

External links


  Results from FactBites:
 
Reduced instruction set computer - Wikipedia, the free encyclopedia (4185 words)
The reduced instruction set computer, or RISC, is a microprocessor CPU design philosophy that favors a smaller and simpler set of instructions that all take about the same amount of time to execute.
Unfortunately, the term "reduced instruction set computer" is often mis-understood as claiming that there are fewer instructions in the instruction set of those machines.
Many in the computer industry criticized that the performance benefits were unlikely to translate into real-world settings due to the decreased memory efficiency of multiple instructions, and that that was the reason no one was using them.
Complex instruction set computer - Wikipedia, the free encyclopedia (417 words)
A complex instruction set computer (CISC) is a microprocessor instruction set architecture (ISA) in which each instruction can execute several low-level operations, such as a load from memory, an arithmetic operation, and a memory store, all in a single instruction.
The term was coined in contrast to reduced instruction set computer (RISC).
Modern "CISC" CPUs, such as recent x86 designs like the Pentium 4, whilst they usually support every instruction that their predecessors did, are designed to work most efficiently with a subset of instructions more resembling a typical "RISC" instruction set.
  More results at FactBites »

 
 

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