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107-462: Precision Architecture RISC ( PA-RISC ) or Hewlett Packard Precision Architecture ( HP/PA or simply HPPA ), is a general purpose computer instruction set architecture (ISA) developed by Hewlett-Packard from the 1980s until the 2000s. The architecture was introduced on 26 February 1986, when the HP 3000 Series 930 and HP 9000 Model 840 computers were launched featuring the first implementation,

214-606: A Harvard memory model , where the instruction stream and the data stream are conceptually separated; this means that modifying the memory 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; CISC processors that have separate instruction and data caches generally keep them synchronized automatically, for backwards compatibility with older processors. Many early RISC designs also shared

321-484: A load–store architecture in which the code for the register-register instructions (for performing arithmetic and tests) are separate from the instructions that access the main memory of the computer. The design of the CPU allows RISC computers few simple addressing modes and predictable instruction times that simplify design of the system as a whole. The conceptual developments of the RISC computer architecture began with

428-413: A reduced instruction set computer ( RISC ) is a computer architecture designed to simplify the individual instructions given to the computer to accomplish tasks. Compared to the instructions given to a complex instruction set computer (CISC), a RISC computer might require more instructions (more code) in order to accomplish a task because the individual instructions are written in simpler code. The goal

535-750: A 24-bit high-speed processor to use as the basis for a digital telephone switch . To reach their goal of switching 1 million calls per hour (300 per second) they calculated that the CPU required performance on the order of 12 million instructions per second (MIPS), compared to their fastest mainframe machine of the time, the 370/168 , which performed at 3.5 MIPS. The design was based on a study of IBM's extensive collection of statistics gathered from their customers. This demonstrated that code in high-performance settings made extensive use of processor registers , and that they often ran out of them. This suggested that additional registers would improve performance. Additionally, they noticed that compilers generally ignored

642-408: A 5-bit number, for 15 bits. If one of these registers is replaced by an immediate, there is still lots of room to encode the two remaining registers and the opcode. Common instructions found in multi-word systems, like INC and DEC , which reduce the number of words that have to be read before performing the instruction, are unnecessary in RISC as they can be accomplished with a single register and

749-511: A SIMD processor somewhere in its architecture. The PlayStation 2 was unusual in that one of its vector-float units could function as an autonomous DSP executing its own instruction stream, or as a coprocessor driven by ordinary CPU instructions. 3D graphics applications tend to lend themselves well to SIMD processing as they rely heavily on operations with 4-dimensional vectors. Microsoft 's Direct3D 9.0 now chooses at runtime processor-specific implementations of its own math operations, including

856-404: A SIMD processor there are two improvements to this process. For one the data is understood to be in blocks, and a number of values can be loaded all at once. Instead of a series of instructions saying "retrieve this pixel, now retrieve the next pixel", a SIMD processor will have a single instruction that effectively says "retrieve n pixels" (where n is a number that varies from design to design). For

963-524: A barebones core sufficient for a small embedded processor to supercomputer and cloud computing use with standard and chip designer–defined extensions and coprocessors. It has been tested in silicon design with the ROCKET SoC , which is also available as an open-source processor generator in the CHISEL language. In the early 1980s, significant uncertainties surrounded the RISC concept. One concern involved

1070-400: A better balancing of pipeline stages than before, making RISC pipelines significantly more efficient and allowing higher clock frequencies . Yet another impetus of both RISC and other designs came from practical measurements on real-world programs. Andrew Tanenbaum summed up many of these, demonstrating that processors often had oversized immediates. For instance, he showed that 98% of all

1177-686: A branch instruction is executed before the program's control flow is transferred to the target instruction of the branch. An HP Precision processor also includes a Processor Status Word (PSW) register. The PSW register contains various flags that enable virtual addressing, protection, interruptions , and other status information. The number of floating-point registers was doubled in the 1.1 version to 32 once it became apparent that 16 were inadequate and restricted performance. The architects included Allen Baum, Hans Jeans, Michael J. Mahon, Ruby Bei-Loh Lee , Russel Kao, Steve Muchnick , Terrence C. Miller, David Fotland, and William S. Worley. The first implementation

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1284-649: A bus, and later integrated on-chip. Only the PA-7100LC and PA-7300LC have L2 caches. Another innovation of the PA-RISC is the addition of vector instructions ( SIMD ) in the form of MAX , which were first introduced on the PA-7100LC. Precision RISC Organization , an industry group led by HP, was founded in 1992, to promote the PA-RISC architecture. Members included Convex , Hitachi , Hughes Aircraft , Mitsubishi , NEC , OKI , Prime , Stratus , Yokogawa , Red Brick Software , and Allegro Consultants, Inc. The ISA

1391-527: A common operation in many multimedia applications. One example would be changing the brightness of an image. Each pixel of an image consists of three values for the brightness of the red (R), green (G) and blue (B) portions of the color. To change the brightness, the R, G and B values are read from memory, a value is added to (or subtracted from) them, and the resulting values are written back out to memory. Audio DSPs would likewise, for volume control, multiply both Left and Right channels simultaneously. With

1498-452: A different opcode. In contrast, a 32-bit machine has ample room to encode an immediate value, and doing so avoids the need to do a second memory read to pick up the value. This is why many RISC processors allow a 12- or 13-bit constant to be encoded directly into the instruction word. Assuming a 13-bit constant area, as is the case in the MIPS and RISC designs, another 19 bits are available for

1605-485: A few "vector registers" that use the same interfaces across all CPUs with this instruction set. The hardware handles all alignment issues and "strip-mining" of loops. Machines with different vector sizes would be able to run the same code. LLVM calls this vector type "vscale". An order of magnitude increase in code size is not uncommon, when compared to equivalent scalar or equivalent vector code, and an order of magnitude or greater effectiveness (work done per instruction)

1712-493: A number of additional points. Among these was the fact that programs spent a significant amount of time performing subroutine calls and returns, and it seemed there was the potential to improve overall performance by speeding these calls. This led the Berkeley design to select a method known as register windows which can significantly improve subroutine performance although at the cost of some complexity. They also noticed that

1819-598: A paper on ways to improve microcoding, but later changed his mind and decided microcode itself was the problem. With funding from the DARPA VLSI Program , Patterson started the Berkeley RISC effort. The Program, practically unknown today, led to a huge number of advances in chip design, fabrication, and even computer graphics. Considering a variety of programs from their BSD Unix variant, the Berkeley team found, as had IBM, that most programs made no use of

1926-484: A particular strategy for implementing some RISC designs, and modern RISC designs generally do away with it (such as PowerPC and more recent versions of SPARC and MIPS). Some aspects attributed to the first RISC- labeled designs around 1975 include the observations that the memory-restricted compilers of the time were often unable to take advantage of features intended to facilitate manual assembly coding, and that complex addressing modes take many cycles to perform due to

2033-413: A pipelined processor and for code generation by an optimizing compiler. A common misunderstanding of the phrase "reduced instruction set computer" is that instructions are simply eliminated, resulting in a smaller set of instructions. In fact, over the years, RISC instruction sets have grown in size, and today many of them have a larger set of instructions than many CISC CPUs. Some RISC processors such as

2140-417: A powerful tool in real-time video processing applications like conversion between various video standards and frame rates ( NTSC to/from PAL , NTSC to/from HDTV formats, etc.), deinterlacing , image noise reduction , adaptive video compression , and image enhancement. A more ubiquitous application for SIMD is found in video games : nearly every modern video game console since 1998 has incorporated

2247-469: A reasonably sized constant in a 32-bit instruction word. Since many real-world programs spend most of their time executing simple operations, some researchers decided to focus on making those operations as fast as possible. The clock rate of a CPU is limited by the time it takes to execute the slowest sub-operation of any instruction; decreasing that cycle-time often accelerates the execution of other instructions. The focus on "reduced instructions" led to

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2354-402: A safe fallback mechanism on unsupported CPUs to simple loops. Instead of providing an SIMD datatype, compilers can also be hinted to auto-vectorize some loops, potentially taking some assertions about the lack of data dependency. This is not as flexible as manipulating SIMD variables directly, but is easier to use. OpenMP 4.0+ has a #pragma omp simd hint. This OpenMP interface has replaced

2461-506: A sequence of simpler internal instructions. In the 68k, a full 1 ⁄ 3 of the transistors were used for this microcoding. In 1979, David Patterson was sent on a sabbatical from the University of California, Berkeley to help DEC's west-coast team improve the VAX microcode. Patterson was struck by the complexity of the coding process and concluded it was untenable. He first wrote

2568-503: A sequence of simpler operations doing the same thing. This was in part an effect of the fact that many designs were rushed, with little time to optimize or tune every instruction; only those used most often were optimized, and a sequence of those instructions could be faster than a less-tuned instruction performing an equivalent operation as that sequence. One infamous example was the VAX 's INDEX instruction. The Berkeley work also turned up

2675-457: A single complex instruction such as STRING MOVE , but hide those details from the compiler. The internal operations of a RISC processor are "exposed to the compiler", leading to the backronym 'Relegate Interesting Stuff to the Compiler'. Most RISC architectures have fixed-length instructions and a simple encoding, which simplifies fetch, decode, and issue logic considerably. This is among

2782-482: A single data memory cycle—compared to the "complex instructions" of CISC CPUs that may require dozens of data memory cycles in order to execute a single instruction. The term load–store architecture is sometimes preferred. Another way of looking at the RISC/CISC debate is to consider what is exposed to the compiler. In a CISC processor, the hardware may internally use registers and flag bit in order to implement

2889-556: A single instruction without any overhead. This is similar to C and C++ intrinsics. Benchmarks for 4×4 matrix multiplication , 3D vertex transformation , and Mandelbrot set visualization show near 400% speedup compared to scalar code written in Dart. McCutchan's work on Dart, now called SIMD.js, has been adopted by ECMAScript and Intel announced at IDF 2013 that they are implementing McCutchan's specification for both V8 and SpiderMonkey . However, by 2017, SIMD.js has been taken out of

2996-616: A time, using a hypercube-connected network or processor-dedicated RAM to find its operands. Supercomputing moved away from the SIMD approach when inexpensive scalar MIMD approaches based on commodity processors such as the Intel i860 XP became more powerful, and interest in SIMD waned. The current era of SIMD processors grew out of the desktop-computer market rather than the supercomputer market. As desktop processors became powerful enough to support real-time gaming and audio/video processing during

3103-417: A variety of reasons, this can take much less time than retrieving each pixel individually, as with a traditional CPU design. Another advantage is that the instruction operates on all loaded data in a single operation. In other words, if the SIMD system works by loading up eight data points at once, the add operation being applied to the data will happen to all eight values at the same time. This parallelism

3210-613: A very small set of instructions—but these designs are very different from classic RISC designs, so they have been given other names such as minimal instruction set computer (MISC) or transport triggered architecture (TTA). RISC architectures have traditionally had few successes in the desktop PC and commodity server markets, where the x86 -based platforms remain the dominant processor architecture. However, this may change, as ARM-based processors are being developed for higher performance systems. Manufacturers including Cavium , AMD, and Qualcomm have released server processors based on

3317-488: A wide set of nonstandard extensions, including Cilk 's #pragma simd , GCC's #pragma GCC ivdep , and many more. Consumer software is typically expected to work on a range of CPUs covering multiple generations, which could limit the programmer's ability to use new SIMD instructions to improve the computational performance of a program. The solution is to include multiple versions of the same code that uses either older or newer SIMD technologies, and pick one that best fits

PA-RISC - Misplaced Pages Continue

3424-567: Is achievable with Vector ISAs. ARM's Scalable Vector Extension takes another approach, known in Flynn's Taxonomy as "Associative Processing", more commonly known today as "Predicated" (masked) SIMD. This approach is not as compact as Vector processing but is still far better than non-predicated SIMD. Detailed comparative examples are given in the Vector processing page. Small-scale (64 or 128 bits) SIMD became popular on general-purpose CPUs in

3531-415: Is common for publishers of the SIMD instruction sets to make their own C/C++ language extensions with intrinsic functions or special datatypes (with operator overloading ) guaranteeing the generation of vector code. Intel, AltiVec, and ARM NEON provide extensions widely adopted by the compilers targeting their CPUs. (More complex operations are the task of vector math libraries.) The GNU C Compiler takes

3638-699: Is easier to achieve as only compiler switches need to be changed. Glibc supports LMV and this functionality is adopted by the Intel-backed Clear Linux project. In 2013 John McCutchan announced that he had created a high-performance interface to SIMD instruction sets for the Dart programming language, bringing the benefits of SIMD to web programs for the first time. The interface consists of two types: Instances of these types are immutable and in optimized code are mapped directly to SIMD registers. Operations expressed in Dart typically are compiled into

3745-687: Is heavily SIMD based. Philips , now NXP , developed several SIMD processors named Xetal . The Xetal has 320 16-bit processor elements especially designed for vision tasks. Intel's AVX-512 SIMD instructions process 512 bits of data at once. SIMD instructions are widely used to process 3D graphics, although modern graphics cards with embedded SIMD have largely taken over this task from the CPU. Some systems also include permute functions that re-pack elements inside vectors, making them particularly useful for data processing and compression. They are also used in cryptography. The trend of general-purpose computing on GPUs ( GPGPU ) may lead to wider use of SIMD in

3852-440: Is separate from the parallelism provided by a superscalar processor ; the eight values are processed in parallel even on a non-superscalar processor, and a superscalar processor may be able to perform multiple SIMD operations in parallel. To remedy problems 1 and 5, RISC-V 's vector extension uses an alternative approach: instead of exposing the sub-register-level details to the programmer, the instruction set abstracts them out as

3959-452: Is to offset the need to process more instructions by increasing the speed of each instruction, in particular by implementing an instruction pipeline , which may be simpler to achieve given simpler instructions. The key operational concept of the RISC computer is that each instruction performs only one function (e.g. copy a value from memory to a register). The RISC computer usually has many (16 or 32) high-speed, general-purpose registers with

4066-550: The Adapteva Epiphany , have an optional short, feature-reduced compressed instruction set . Generally, these instructions expose a smaller number of registers and fewer bits for immediate values, and often use a two-operand format to eliminate one register number from instructions. A two-operand format in a system with 16 registers requires 8 bits for register numbers, leaving another 8 for an opcode or other uses. The SH5 also follows this pattern, albeit having evolved in

4173-599: The Cray-1 (1977). The first era of modern SIMD computers was characterized by massively parallel processing -style supercomputers such as the Thinking Machines CM-1 and CM-2 . These computers had many limited-functionality processors that would work in parallel. For example, each of 65,536 single-bit processors in a Thinking Machines CM-2 would execute the same instruction at the same time, allowing, for instance, to logically combine 65,536 pairs of bits at

4280-623: The DEC Alpha , AMD Am29000 , Intel i860 and i960 , Motorola 88000 , IBM POWER , and, slightly later, the IBM/Apple/Motorola PowerPC . Many of these have since disappeared due to them often offering no competitive advantage over others of the same era. Those that remain are often used only in niche markets or as parts of other systems; of the designs from these traditional vendors, only SPARC and POWER have any significant remaining market. The ARM architecture has been

4387-700: The FPU and MMX registers . Compilers also often lacked support, requiring programmers to resort to assembly language coding. SIMD on x86 had a slow start. The introduction of 3DNow! by AMD and SSE by Intel confused matters somewhat, but today the system seems to have settled down (after AMD adopted SSE) and newer compilers should result in more SIMD-enabled software. Intel and AMD now both provide optimized math libraries that use SIMD instructions, and open source alternatives like libSIMD , SIMDx86 and SLEEF have started to appear (see also libm ). Apple Computer had somewhat more success, even though they entered

PA-RISC - Misplaced Pages Continue

4494-555: The Fugaku . A number of systems, going back to the 1960s, have been credited as the first RISC architecture, partly based on their use of the load–store approach. The term RISC was coined by David Patterson of the Berkeley RISC project, although somewhat similar concepts had appeared before. The CDC 6600 designed by Seymour Cray in 1964 used a load–store architecture with only two addressing modes (register+register, and register+immediate constant) and 74 operation codes, with

4601-627: The IBM 801 project in the late 1970s, but these were not immediately put into use. Designers in California picked up the 801 concepts in two seminal projects, Stanford MIPS and Berkeley RISC . These were commercialized in the 1980s as the MIPS and SPARC systems. IBM eventually produced RISC designs based on further work on the 801 concept, the IBM POWER architecture , PowerPC , and Power ISA . As

4708-529: The RT PC —was less competitive than others, but the success of SPARC renewed interest within IBM, which released new RISC systems by 1990 and by 1995 RISC processors were the foundation of a $ 15 billion server industry. By the later 1980s, the new RISC designs were easily outperforming all traditional designs by a wide margin. At that point, all of the other vendors began RISC efforts of their own. Among these were

4815-596: The Spectrum program. HP planned to use Spectrum to move all of their non-PC compatible machines to a single RISC CPU family. In early 1982, work on the Precision Architecture began at HP Laboratories, defining the instruction set and virtual memory system. Development of the first TTL implementation started in April 1983. With simulation of the processor having completed in 1983, a final processor design

4922-479: The 1990s, demand grew for this particular type of computing power, and microprocessor vendors turned to SIMD to meet the demand. Hewlett-Packard introduced MAX instructions into PA-RISC 1.1 desktops in 1994 to accelerate MPEG decoding. Sun Microsystems introduced SIMD integer instructions in its " VIS " instruction set extensions in 1995, in its UltraSPARC I microprocessor. MIPS followed suit with their similar MDMX system. The first widely deployed desktop SIMD

5029-707: The ARM architecture. ARM further partnered with Cray in 2017 to produce an ARM-based supercomputer. On the desktop, Microsoft announced that it planned to support the PC version of Windows 10 on Qualcomm Snapdragon -based devices in 2017 as part of its partnership with Qualcomm. These devices will support Windows applications compiled for 32-bit x86 via an x86 processor emulator that translates 32-bit x86 code to ARM64 code . Apple announced they will transition their Mac desktop and laptop computers from Intel processors to internally developed ARM64-based SoCs called Apple silicon ;

5136-597: The Berkeley RISC-II system. The US government Committee on Innovations in Computing and Communications credits the acceptance of the viability of the RISC concept to the success of the SPARC system. By 1989 many RISC CPUs were available; competition lowered their price to $ 10 per MIPS in large quantities, much less expensive than the sole sourced Intel 80386 . The performance of IBM's RISC CPU—only available in

5243-583: The ECMAScript standard queue in favor of pursuing a similar interface in WebAssembly . As of August 2020, the WebAssembly interface remains unfinished, but its portable 128-bit SIMD feature has already seen some use in many engines. Emscripten, Mozilla's C/C++-to-JavaScript compiler, with extensions can enable compilation of C++ programs that make use of SIMD intrinsics or GCC-style vector code to

5350-562: The GCC extension. LLVM's libcxx seems to implement it. For GCC and libstdc++, a wrapper library that builds on top of the GCC extension is available. Microsoft added SIMD to .NET in RyuJIT. The System.Numerics.Vector package, available on NuGet, implements SIMD datatypes. Java also has a new proposed API for SIMD instructions available in OpenJDK 17 in an incubator module. It also has

5457-448: The ISA, who in partnership with TI, GEC, Sharp, Nokia, Oracle and Digital would develop low-power and embedded RISC designs, and target those market segments, which at the time were niche. With the rise in mobile, automotive, streaming, smart device computing, ARM became the most widely used ISA, the company estimating almost half of all CPUs shipped in history have been ARM. Confusion around

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5564-592: The PowerPC have instruction sets as large as the CISC IBM System/370 , for example; conversely, the DEC PDP-8 —clearly a CISC CPU because many of its instructions involve multiple memory accesses—has only 8 basic instructions and a few extended instructions. The term "reduced" in that phrase was intended to describe the fact that the amount of work any single instruction accomplishes is reduced—at most

5671-579: The SIMD API of JavaScript, resulting in equivalent speedups compared to scalar code. It also supports (and now prefers) the WebAssembly 128-bit SIMD proposal. It has generally proven difficult to find sustainable commercial applications for SIMD-only processors. One that has had some measure of success is the GAPP , which was developed by Lockheed Martin and taken to the commercial sector by their spin-off Teranex . The GAPP's recent incarnations have become

5778-540: The SIMD market later than the rest. AltiVec offered a rich system and can be programmed using increasingly sophisticated compilers from Motorola , IBM and GNU , therefore assembly language programming is rarely needed. Additionally, many of the systems that would benefit from SIMD were supplied by Apple itself, for example iTunes and QuickTime . However, in 2006, Apple computers moved to Intel x86 processors. Apple's APIs and development tools ( XCode ) were modified to support SSE2 and SSE3 as well as AltiVec. Apple

5885-613: The TS1. HP stopped selling PA-RISC-based HP 9000 systems at the end of 2008 but supported servers running PA-RISC chips until 2013. PA-RISC was succeeded by the Itanium (originally IA-64) ISA, jointly developed by HP and Intel . In the late 1980s, HP was building four series of computers, all based on CISC CPUs. One line was the IBM PC compatible Intel i286 -based Vectra Series, started in 1986. All others were non- Intel systems. One of them

5992-535: The VAX. 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. As the RISC project began to become known in Silicon Valley , a similar project began at Stanford University in 1981. This MIPS project grew out of a graduate course by John L. Hennessy , produced a functioning system in 1983, and could run simple programs by 1984. The MIPS approach emphasized an aggressive clock cycle and

6099-561: The basic clock cycle being 10 times faster than the memory access time. Partly due to the optimized load–store architecture of the CDC 6600, Jack Dongarra says that it can be considered a forerunner of modern RISC systems, although a number of other technical barriers needed to be overcome for the development of a modern RISC system. Michael J. Flynn views the first RISC system as the IBM 801 design, begun in 1975 by John Cocke and completed in 1980. The 801 developed out of an effort to build

6206-472: The characteristic of having a branch delay slot , 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

6313-418: The code to "clone" functions, while ICC does so automatically (under the command-line option /Qax ). The Rust programming language also supports FMV. The setup is similar to GCC and Clang in that the code defines what instruction sets to compile for, but cloning is manually done via inlining. As using FMV requires code modification on GCC and Clang, vendors more commonly use library multi-versioning: this

6420-441: The constants in a program would fit in 13 bits , yet many CPU designs dedicated 16 or 32 bits to store them. This suggests that, to reduce the number of memory accesses, a fixed length machine could store constants in unused bits of the instruction word itself, so that they would be immediately ready when the CPU needs them (much like immediate addressing in a conventional design). This required small opcodes in order to leave room for

6527-423: The definition of RISC deriving from the formulation of the term, along with the tendency to opportunistically categorize processor architectures with relatively few instructions (or groups of instructions) as RISC architectures, led to attempts to define RISC as a design philosophy. One attempt to do so was expressed as the following: A RISC processor has an instruction set that is designed for efficient execution by

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6634-535: The development labs. These machines ran MPE-XL . The HP 9000 machines were soon upgraded with the PA-RISC processor as well, running the HP-UX version of Unix . Other operating systems ported to the PA-RISC architecture include Linux , OpenBSD , NetBSD , OSF/1 , NeXTSTEP , and ChorusOS . An interesting aspect of the PA-RISC line is that most of its generations have no level 2 cache . Instead large level 1 caches are used, initially as separate chips connected by

6741-472: The early 1980s, leading, for example, to the iron law of processor performance . Since 2010, a new open standard instruction set architecture (ISA), Berkeley RISC-V , has been under development at the University of California, Berkeley, for research purposes and as a free alternative to proprietary ISAs. As of 2014, version 2 of the user space ISA is fixed. The ISA is designed to be extensible from

6848-643: The early 1980s. Few of these designs began by using RISC microprocessors . The varieties of RISC processor design include the ARC processor, the DEC Alpha, the AMD Am29000 , the ARM architecture, the Atmel AVR , Blackfin , Intel i860 , Intel i960 , LoongArch , Motorola 88000 , the MIPS architecture, PA-RISC, Power ISA, RISC-V , SuperH , and SPARC. RISC processors are used in supercomputers , such as

6955-594: The early 1990s and continued through 1997 and later with Motion Video Instructions (MVI) for Alpha . SIMD instructions can be found, to one degree or another, on most CPUs, including IBM 's AltiVec and SPE for PowerPC , HP 's PA-RISC Multimedia Acceleration eXtensions (MAX), Intel 's MMX and iwMMXt , SSE , SSE2 , SSE3 SSSE3 and SSE4.x , AMD 's 3DNow! , ARC 's ARC Video subsystem, SPARC 's VIS and VIS2, Sun 's MAJC , ARM 's Neon technology, MIPS ' MDMX (MaDMaX) and MIPS-3D . The IBM, Sony, Toshiba co-developed Cell Processor 's SPU 's instruction set

7062-509: The extensions a step further by abstracting them into a universal interface that can be used on any platform by providing a way of defining SIMD datatypes. The LLVM Clang compiler also implements the feature, with an analogous interface defined in the IR. Rust's packed_simd crate (and the experimental std::sims ) uses this interface, and so does Swift 2.0+. C++ has an experimental interface std::experimental::simd that works similarly to

7169-591: The first such computers, using the Apple M1 processor, were released in November 2020. Macs with Apple silicon can run x86-64 binaries with Rosetta 2 , an x86-64 to ARM64 translator. Outside of the desktop arena, however, the ARM RISC architecture is in widespread use in smartphones, tablets and many forms of embedded devices. While early RISC designs differed significantly from contemporary CISC designs, by 2000

7276-465: The future. Adoption of SIMD systems in personal computer software was at first slow, due to a number of problems. One was that many of the early SIMD instruction sets tended to slow overall performance of the system due to the re-use of existing floating point registers. Other systems, like MMX and 3DNow! , offered support for data types that were not interesting to a wide audience and had expensive context switching instructions to switch between using

7383-474: The ground up with no separate scalar registers. Ziilabs produced an SIMD type processor for use on mobile devices, such as media players and mobile phones. Larger scale commercial SIMD processors are available from ClearSpeed Technology, Ltd. and Stream Processors, Inc. ClearSpeed 's CSX600 (2004) has 96 cores each with two double-precision floating point units while the CSX700 (2008) has 192. Stream Processors

7490-509: The highest-performing CPUs in the RISC line were almost indistinguishable from the highest-performing CPUs in the CISC line. RISC architectures are now used across a range of platforms, from smartphones and tablet computers to some of the world's fastest supercomputers such as Fugaku , the fastest on the TOP500 list as of November 2020 , and Summit , Sierra , and Sunway TaihuLight ,

7597-413: The immediate value 1. The original RISC-I format remains a canonical example of the concept. It uses 7 bits for the opcode and a 1-bit flag for conditional codes, the following 5 bits for the destination register, and the next five for the first operand. This leaves 14 bits, the first of which indicates whether the following 13 contain an immediate value or uses only five of them to indicate a register for

7704-403: The instruction encoding. This leaves ample room to indicate both the opcode and one or two registers. Register-to-register operations, mostly math and logic, require enough bits to encode the two or three registers being used. Most processors use the three-operand format, of the form A = B + C , in which case three registers numbers are needed. If the processor has 32 registers, each one requires

7811-445: The instruction word which could then be used to select among a larger set of registers. The telephone switch program was canceled in 1975, but by then the team had demonstrated that the same design would offer significant performance gains running just about any code. In simulations, they showed that a compiler tuned to use registers wherever possible would run code about three times as fast as traditional designs. Somewhat surprisingly,

7918-428: The large variety of instructions in the 68k. Patterson's early work pointed out an important problem with the traditional "more is better" approach; even those instructions that were critical to overall performance were being delayed by their trip through the microcode. If the microcode was removed, the programs would run faster. And since the microcode ultimately took a complex instruction and broke it into steps, there

8025-482: The late 1970s, the 801 had become well-known in the industry. This coincided with new fabrication techniques that were allowing more complex chips to come to market. The Zilog Z80 of 1976 had 8,000 transistors, whereas the 1979 Motorola 68000 (68k) had 68,000. These newer designs generally used their newfound complexity to expand the instruction set to make it more orthogonal. Most, like the 68k, used microcode to do this, reading instructions and re-implementing them as

8132-494: The main goals of the RISC approach. Some of this is possible only due to the contemporary move to 32-bit formats. For instance, in a typical program, over 30% of all the numeric constants are either 0 or 1, 95% will fit in one byte, and 99% in a 16-bit value. When computers were based on 8- or 16-bit words, it would be difficult to have an immediate combined with the opcode in a single memory word, although certain instructions like increment and decrement did this implicitly by using

8239-422: The majority of mathematical instructions were simple assignments; only 1 ⁄ 3 of them actually performed an operation like addition or subtraction. But when those operations did occur, they tended to be slow. This led to far more emphasis on the underlying arithmetic data unit, as opposed to previous designs where the majority of the chip was dedicated to control and microcode. The resulting Berkeley RISC

8346-506: The mid-1980s. The Acorn ARM1 appeared in April 1985, MIPS R2000 appeared in January 1986, followed shortly thereafter by Hewlett-Packard 's PA-RISC in some of their computers. In the meantime, the Berkeley effort had become so well known that it eventually became the name for the entire concept. In 1987 Sun Microsystems began shipping systems with the SPARC processor, directly based on

8453-563: The most significant characteristics of RISC processors was that external memory was only accessible by a load or store instruction. All other instructions were limited to internal registers. This simplified many aspects of processor design: allowing instructions to be fixed-length, simplifying pipelines, and isolating the logic for dealing with the delay in completing a memory access (cache miss, etc.) to only two instructions. This led to RISC designs being referred to as load–store architectures. Some CPUs have been specifically designed to have

8560-657: The most widely adopted RISC ISA, initially intended to deliver higher-performance desktop computing, at low cost, and in a restricted thermal package, such as in the Acorn Archimedes , while featuring in the Super Computer League tables , its initial, relatively, lower power and cooling implementation was soon adapted to embedded applications, such as laser printer raster image processing. Acorn, in partnership with Apple Inc, and VLSI, creating ARM Ltd, in 1990, to share R&D costs and find new markets for

8667-428: The newer architectures are then considered "short-vector" architectures, as earlier SIMD and vector supercomputers had vector lengths from 64 to 64,000. A modern supercomputer is almost always a cluster of MIMD computers, each of which implements (short-vector) SIMD instructions. An application that may take advantage of SIMD is one where the same value is being added to (or subtracted from) a large number of data points,

8774-404: The next three on that list. Single instruction, multiple data Such machines exploit data level parallelism , but not concurrency : there are simultaneous (parallel) computations, but each unit performs the exact same instruction at any given moment (just with different data). SIMD is particularly applicable to common tasks such as adjusting the contrast in a digital image or adjusting

8881-540: The opcode was 0 and the last 6 bits contained the actual code; those that used an immediate value used the normal opcode field at the front. One drawback of 32-bit instructions is reduced code density, which is more adverse a characteristic in embedded computing than it is in the workstation and server markets RISC architectures were originally designed to serve. To address this problem, several architectures, such as SuperH (1992), ARM thumb (1994), MIPS16e (2004), Power Variable Length Encoding ISA (2006), RISC-V , and

8988-531: The opposite direction, having added longer 32-bit instructions to an original 16-bit encoding. The most characteristic aspect of RISC is executing at least one instruction per cycle . Single-cycle operation is described as "the rapid execution of simple functions that dominate a computer's instruction stream", thus seeking to deliver an average throughput approaching one instruction per cycle for any single instruction stream. Other features of RISC architectures include: RISC designs are also more likely to feature

9095-570: The projects matured, many similar designs, produced in the mid-to-late 1980s and early 1990s, such as ARM , PA-RISC , and Alpha , created central processing units that increased the commercial utility of the Unix workstation and of embedded processors in the laser printer , the router , and similar products. In the minicomputer market, companies that included Celerity Computing , Pyramid Technology , and Ridge Computers began offering systems designed according to RISC or RISC-like principles in

9202-497: The required additional memory accesses. It was argued that such functions would be better performed by sequences of simpler instructions if this could yield implementations small enough to leave room for many registers, reducing the number of slow memory accesses. In these simple designs, most instructions are of uniform length and similar structure, arithmetic operations are restricted to CPU registers and only separate load and store instructions access memory. These properties enable

9309-402: The resulting machine being called a "reduced instruction set computer" (RISC). The goal was to make instructions so simple that they could easily be pipelined, in order to achieve a single clock throughput at high frequencies . This contrasted with CISC designs whose "crucial arithmetic operations and register transfers" were considered difficult to pipeline. Later, it was noted that one of

9416-508: The same code would run about 50% faster even on existing machines due to the improved register use. In practice, their experimental PL/8 compiler, a slightly cut-down version of PL/I , consistently produced code that ran much faster on their existing mainframes. A 32-bit version of the 801 was eventually produced in a single-chip form as the IBM ROMP in 1981, which stood for 'Research OPD [Office Products Division] Micro Processor'. This CPU

9523-475: The second half of the 1980s, and led the designers of the MIPS-X to put it this way in 1987: The goal of any instruction format should be: 1. simple decode, 2. simple decode, and 3. simple decode. Any attempts at improved code density at the expense of CPU performance should be ridiculed at every opportunity. Competition between RISC and conventional CISC approaches was also the subject of theoretical analysis in

9630-408: The second operand. A more complex example is the MIPS encoding, which used only 6 bits for the opcode, followed by two 5-bit registers. The remaining 16 bits could be used in two ways, one as a 16-bit immediate value, or as a 5-bit shift value (used only in shift operations, otherwise zero) and the remaining 6 bits as an extension on the opcode. In the case of register-to-register arithmetic operations,

9737-609: The use of SIMD-capable instructions. A later processor that used vector processing is the Cell Processor used in the Playstation 3, which was developed by IBM in cooperation with Toshiba and Sony . It uses a number of SIMD processors (a NUMA architecture, each with independent local store and controlled by a general purpose CPU) and is geared towards the huge datasets required by 3D and video processing applications. It differs from traditional ISAs by being SIMD from

9844-459: The use of memory; a single instruction from a traditional processor like the Motorola 68k may be written out as perhaps a half dozen of the simpler RISC instructions. In theory, this could slow the system down as it spent more time fetching instructions from memory. But by the mid-1980s, the concepts had matured enough to be seen as commercially viable. Commercial RISC designs began to emerge in

9951-514: The use of the pipeline, making sure it could be run as "full" as possible. The MIPS system was followed by the MIPS-X and in 1984 Hennessy and his colleagues formed MIPS Computer Systems to produce the design commercially. The venture resulted in a new architecture that was also called MIPS and the R2000 microprocessor in 1985. The overall philosophy of the RISC concept was widely understood by

10058-482: The user's CPU at run-time ( dynamic dispatch ). There are two main camps of solutions: FMV, manually coded in assembly language, is quite commonly used in a number of performance-critical libraries such as glibc and libjpeg-turbo. Intel C++ Compiler , GNU Compiler Collection since GCC 6, and Clang since clang 7 allow for a simplified approach, with the compiler taking care of function duplication and selection. GCC and clang requires explicit target_clones labels in

10165-441: The vast majority of the available instructions, especially orthogonal addressing modes. Instead, they selected the fastest version of any given instruction and then constructed small routines using it. This suggested that the majority of instructions could be removed without affecting the resulting code. These two conclusions worked in concert; removing instructions would allow the instruction opcodes to be shorter, freeing up bits in

10272-530: The volume of digital audio . Most modern CPU designs include SIMD instructions to improve the performance of multimedia use. SIMD has three different subcategories in Flynn's 1972 Taxonomy , one of which is SIMT . SIMT should not be confused with software threads or hardware threads , both of which are task time-sharing (time-slicing). SIMT is true simultaneous parallel hardware-level execution. Modern graphics processing units (GPUs) are often wide SIMD implementations. The first use of SIMD instructions

10379-495: The window "down" by eight, to the set of eight registers used by that procedure, and the return moves the window back. The Berkeley 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, with estimated performance being higher than

10486-498: Was based on gaining performance through the use of pipelining and aggressive use of register windowing. In a traditional 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., eight, at any one time. A program that limits itself to eight registers per procedure can make very fast procedure calls : The call simply moves

10593-479: Was delivered to software developers in July 1984. Systems prototyping followed, with "lab prototypes" being produced in 1985 and product prototypes in 1986. The first processors were introduced in products during 1986. It has thirty-two 32-bit integer registers and sixteen 64-bit floating-point registers. The HP Precision Architecture has a single branch delay slot . This means that the instruction immediately following

10700-468: Was designed for "mini" tasks, and found use in peripheral interfaces and channel controllers on later IBM computers. It was also used as the CPU in the IBM RT PC in 1986, which turned out to be a commercial failure. Although the 801 did not see widespread use in its original form, it inspired many research projects, including ones at IBM that would eventually lead to the IBM POWER architecture . By

10807-583: Was extended in 1996 to 64 bits, with this revision named PA-RISC 2.0. PA-RISC 2.0 also added fused multiply–add instructions, which help certain floating-point intensive algorithms, and the MAX-2 SIMD extension, which provides instructions for accelerating multimedia applications. The first PA-RISC 2.0 implementation was the PA-8000 , which was introduced in January 1996. Reduced instruction set computer In electronics and computer science ,

10914-712: Was in the ILLIAC IV , which was completed in 1966. SIMD was the basis for vector supercomputers of the early 1970s such as the CDC Star-100 and the Texas Instruments ASC , which could operate on a "vector" of data with a single instruction. Vector processing was especially popularized by Cray in the 1970s and 1980s. Vector processing architectures are now considered separate from SIMD computers: Duncan's Taxonomy includes them whereas Flynn's Taxonomy does not, due to Flynn's work (1966, 1972) pre-dating

11021-474: Was no reason the compiler couldn't do this instead. These studies suggested that, even with no other changes, one could make a chip with 1 ⁄ 3 fewer transistors that would run faster. In the original RISC-I paper they noted: Skipping this extra level of interpretation appears to enhance performance while reducing chip size. It was also discovered that, on microcoded implementations of certain architectures, complex operations tended to be slower than

11128-572: Was the HP Series 300 of Motorola 68000 -based workstations , another Series 200 line of technical workstations based on a custom silicon on sapphire (SOS) chip design, the SOS based 16-bit HP 3000 classic series, and finally the HP 9000 Series 500 minicomputers , based on their own (16- and 32-bit) FOCUS microprocessor. The Precision Architecture is the result of what was known inside Hewlett-Packard as

11235-453: Was the TS1, a central processing unit built from discrete transistor–transistor logic ( 74F TTL ) devices. Later implementations were multi-chip VLSI designs fabricated in NMOS processes (NS1 and NS2) and CMOS (CS1 and PCX). They were first used in a new series of HP 3000 machines in the late 1980s – the 930 and 950, commonly known at the time as Spectrum systems, the name given to them in

11342-594: Was the dominant purchaser of PowerPC chips from IBM and Freescale Semiconductor . Even though Apple has stopped using PowerPC processors in their products, further development of AltiVec is continued in several PowerPC and Power ISA designs from Freescale and IBM. SIMD within a register , or SWAR , is a range of techniques and tricks used for performing SIMD in general-purpose registers on hardware that does not provide any direct support for SIMD instructions. This can be used to exploit parallelism in certain algorithms even on hardware that does not support SIMD directly. It

11449-911: Was with Intel's MMX extensions to the x86 architecture in 1996. This sparked the introduction of the much more powerful AltiVec system in the Motorola PowerPC and IBM's POWER systems. Intel responded in 1999 by introducing the all-new SSE system. Since then, there have been several extensions to the SIMD instruction sets for both architectures. Advanced vector extensions AVX, AVX2 and AVX-512 are developed by Intel. AMD supports AVX, AVX2 , and AVX-512 in their current products. All of these developments have been oriented toward support for real-time graphics, and are therefore oriented toward processing in two, three, or four dimensions, usually with vector lengths of between two and sixteen words, depending on data type and architecture. When new SIMD architectures need to be distinguished from older ones,

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