Microarchitecture and Microprocessor

In computer engineering, microarchitecture (sometimes abbreviated to µarch or uarch), also called computer organization, is the way a giveninstruction set architecture (ISA) is implemented on a processor. A given ISA may be implemented with different microarchitectures (Dell XPS M1210 Battery) http://www.hdd-shop.co.uk .

Implementations might vary due to different goals of a given design or due to shifts in technology.Computer architecture is the combination of microarchitecture and instruction set design (Dell Studio XPS 1340 Battery) .

Relation to instruction set architecture

The ISA is roughly the same as the programming model of a processor as seen by an assembly language programmer or compiler writer. The ISA includes the execution model, processor registers, address and data formats among other things (Dell Studio XPS 1640 Battery) .

The microarchitecture includes the constituent parts of the processor and how these interconnect and interoperate to implement the ISA.

The microarchitecture of a machine is usually represented as (more or less detailed) diagrams that describe the interconnections of the various microarchitectual elements of the machine (Dell Vostro 1710 Battery) ,

which may be everything from single gates and registers, to complete arithmetic logic units (ALU)s and even larger elements. These diagrams generally separate the data path (where data is placed) and thecontrol path (which can be said to steer the data).

Each microarchitectural element is in turn represented by a schematic describing the interconnections of logic gates used to implement it (Sony VGP-BPS13 battery) .

Each logic gate is in turn represented by a circuit diagramdescribing the connections of the transistors used to implement it in some particular logic family. Machines with different microarchitectures may have the same instruction set architecture, and thus be capable of executing the same programs (Sony VGP-BPS13/B battery) .

New microarchitectures and/or circuitry solutions, along with advances in semiconductor manufacturing, are what allows newer generations of processors to achieve higher performance while using the same ISA.

In principle, a single microarchitecture could execute several different ISAs with only minor changes to the microcode (Sony VGP-BPS13/S battery) .

Aspects of microarchitecture

The pipelined datapath is the most commonly used datapath design in microarchitecture today. This technique is used in most modern microprocessors, microcontrollers, and DSPs. The pipelined architecture allows multiple instructions to overlap in execution, much like an assembly line (Sony VGP-BPS13A/B battery) .

The pipeline includes several different stages which are fundamental in microarchitecture designs. Some of these stages include instruction fetch, instruction decode, execute, and write back. Some architectures include other stages such as memory access. The design of pipelines is one of the central microarchitectural tasks (Sony VGP-BPS13B/B battery) .

Execution units are also essential to microarchitecture. Execution units include arithmetic logic units (ALU), floating point units (FPU), load/store units, branch prediction, and SIMD. These units perform the operations or calculations of the processor (Sony VGP-BPL9 battery) .

The choice of the number of execution units, their latency and throughput is a central microarchitectural design task. The size, latency, throughput and connectivity of memories within the system are also microarchitectural decisions (Sony VGP-BPS13B/B battery) .

System-level design decisions such as whether or not to include peripherals, such as memory controllers, can be considered part of the microarchitectural design process. This includes decisions on the performance-level and connectivity of these peripherals (Sony VGP-BPL11 battery) .

Unlike architectural design, where achieving a specific performance level is the main goal, microarchitectural design pays closer attention to other constraints. Since microarchitecture design decisions directly affect what goes into a system, attention must be paid to such issues as (Sony VGP-BPL15 battery) :

• Chip area/cost
• Power consumption
• Logic complexity
• Ease of connectivity
• Manufacturability
• Ease of debugging
• Testability (Dell Inspiron E1505 battery)

Microarchitectural concepts

In general, all CPUs, single-chip microprocessors or multi-chip implementations run programs by performing the following steps:

1. Read an instruction and decode it
2. Find any associated data that is needed to process the instruction (Dell Latitude E6400 battery)
3. Process the instruction
4. Write the results out

Complicating this simple-looking series of steps is the fact that the memory hierarchy, which includes caching, main memory and non-volatile storage like hard disks, (where the program instructions and data reside) has always been slower than the processor itself (HP Pavilion dv6000 Battery) .

Step (2) often introduces a lengthy (in CPU terms) delay while the data arrives over the computer bus. A considerable amount of research has been put into designs that avoid these delays as much as possible. Over the years, a central goal was to execute more instructions in parallel, thus increasing the effective execution speed of a program (Sony Vaio VGN-FZ31S battery) .

These efforts introduced complicated logic and circuit structures. Initially these techniques could only be implemented on expensive mainframes or supercomputers due to the amount of circuitry needed for these techniques. As semiconductor manufacturing progressed, more and more of these techniques could be implemented on a single semiconductor chip (Sony VGN-FZ31S battery) .

What follows is a survey of micro-architectural techniques that are common in modern CPUs.

Instruction set choice

Instruction sets have shifted over the years, from originally very simple to sometimes very complex (in various respects) (Hp pavilion dv6000 battery) .

In recent years, load-store architectures, VLIW and EPIC types have been in fashion. Architectures that are dealing with data parallelism include SIMD and Vectors. Some labels used to denote classes of CPU architectures are not particularly descriptive, especially so the CISC label; many early designs retroactively denoted "CISC" are in fact significantly simpler than modern RISC processors (in several respects) (SONY VGN-FZ38M Battery) .

However, the choice of instruction set architecture may greatly affect the complexity of implementing high performance devices. The prominent strategy, used to develop the first RISC processors, was to simplify instructions to a minimum of individual semantic complexity combined with high encoding regularity and simplicity (SONY VGN-FZ31z Battery) .

Such uniform instructions were easily fetched, decoded and executed in a pipelined fashion and a simple strategy to reduce the number of logic levels in order to reach high operating frequencies; instruction cache-memories compensated for the higher operating frequency and inherently low code density while large register sets were used to factor out as much of the (slow) memory accesses as possible (Sony VGN-FZ31Z Battery) .

Instruction pipelining

One of the first, and most powerful, techniques to improve performance is the use of the instruction pipeline. Early processor designs would carry out all of the steps above for one instruction before moving onto the next (SONY VAIO VGN-FZ38M Battery) .

Large portions of the circuitry were left idle at any one step; for instance, the instruction decoding circuitry would be idle during execution and so on.

Pipelines improve performance by allowing a number of instructions to work their way through the processor at the same time (SONY VGN-FZ31E Battery) .

In the same basic example, the processor would start to decode (step 1) a new instruction while the last one was waiting for results. This would allow up to four instructions to be "in flight" at one time, making the processor look four times as fast (SONY VGN-FZ31J Battery) .

Although any one instruction takes just as long to complete (there are still four steps) the CPU as a whole "retires" instructions much faster and can be run at a much higher clock speed.

RISC make pipelines smaller and much easier to construct by cleanly separating each stage of the instruction process and making them take the same amount of time — one cycle (SONY VGN-FZ31M Battery) .

The processor as a whole operates in an assembly line fashion, with instructions coming in one side and results out the other. Due to the reduced complexity of the Classic RISC pipeline, the pipelined core and an instruction cache could be placed on the same size die that would otherwise fit the core alone on a CISC design (SONY VGN-FZ31B Battery) .

This was the real reason that RISC was faster. Early designs like the SPARC andMIPS often ran over 10 times as fast as Intel and Motorola CISC solutions at the same clock speed and price.

Pipelines are by no means limited to RISC designs (SONY VGP-BPS13 Battery) .

By 1986 the top-of-the-line VAX implementation (VAX 8800) was a heavily pipelined design, slightly predating the first commercial MIPS and SPARC designs. Most modern CPUs (even embedded CPUs) are now pipelined, and microcoded CPUs with no pipelining are seen only in the most area-constrained embedded processors (Dell Inspiron 1320 Battery) .

Large CISC machines, from the VAX 8800 to the modern Pentium 4 and Athlon, are implemented with both microcode and pipelines. Improvements in pipelining and caching are the two major microarchitectural advances that have enabled processor performance to keep pace with the circuit technology on which they are based (Dell Inspiron 1320n Battery) .

Cache

It was not long before improvements in chip manufacturing allowed for even more circuitry to be placed on the die, and designers started looking for ways to use it. One of the most common was to add an ever-increasing amount of cache memory on-die (Dell Inspiron 1464 Battery) .

Cache is simply very fast memory, memory that can be accessed in a few cycles as opposed to "many" needed to talk to main memory. The CPU includes a cache controller which automates reading and writing from the cache, if the data is already in the cache it simply "appears," whereas if it is not the processor is "stalled" while the cache controller reads it in (Dell Inspiron 1564 Battery) .

RISC designs started adding cache in the mid-to-late 1980s, often only 4 KB in total. This number grew over time, and typical CPUs now have at least 512 KB, while more powerful CPUs come with 1 or 2 or even 4, 6, 8 or 12 MB, organized in multiple levels of a memory hierarchy. Generally speaking, more cache means more performance, due to reduced stalling (Dell Inspiron 1764 Battery) .

Caches and pipelines were a perfect match for each other. Previously, it didn't make much sense to build a pipeline that could run faster than the access latency of off-chip memory. Using on-chip cache memory instead, meant that a pipeline could run at the speed of the cache access latency, a much smaller length of time (Dell Studio 1450 Battery) .

This allowed the operating frequencies of processors to increase at a much faster rate than that of off-chip memory.

Branch prediction

One barrier to achieving higher performance through instruction-level parallelism stems from pipeline stalls and flushes due to branches (Dell Studio 1457 Battery) .

Normally, whether a conditional branch will be taken isn't known until late in the pipeline as conditional branches depend on results coming from a register. From the time that the processor's instruction decoder has figured out that it has encountered a conditional branch instruction to the time that the deciding register value can be read out (Dell Latitude D610 Battery) ,

the pipeline needs to be stalled for several cycles, or if it's not and the branch is taken, the pipeline needs to be flushed. As clock speeds increase the depth of the pipeline increases with it, and some modern processors may have 20 stages or more. On average, every fifth instruction executed is a branch, so without any intervention, that's a high amount of stalling (Toshiba NB100 Battery) .

Techniques such as branch prediction and speculative execution are used to lessen these branch penalties. Branch prediction is where the hardware makes educated guesses on whether a particular branch will be taken. In reality one side or the other of the branch will be called much more often than the other (Toshiba Satellite M65 battery) .

Modern designs have rather complex statistical prediction systems, which watch the results of past branches to predict the future with greater accuracy. The guess allows the hardware to prefetch instructions without waiting for the register read (Toshiba Satellite M60 battery) .

Speculative execution is a further enhancement in which the code along the predicted path is not just prefetched but also executed before it is known whether the branch should be taken or not. This can yield better performance when the guess is good, with the risk of a huge penalty when the guess is bad because instructions need to be undone (Dell Latitude D830 Battery) .

Superscalar

Even with all of the added complexity and gates needed to support the concepts outlined above, improvements in semiconductor manufacturing soon allowed even more logic gates to be used.

In the outline above the processor processes parts of a single instruction at a time (Dell Latitude D620 Battery) .

Computer programs could be executed faster if multiple instructions were processed simultaneously. This is whatsuperscalar processors achieve, by replicating functional units such as ALUs. The replication of functional units was only made possible when the die area of a single-issue processor no longer stretched the limits of what could be reliably manufactured (Dell Studio 1735 Battery) .

By the late 1980s, superscalar designs started to enter the market place.

In modern designs it is common to find two load units, one store (many instructions have no results to store), two or more integer math units, two or more floating point units, and often a SIMD unit of some sort (Dell Inspiron Mini 10 Battery) .

The instruction issue logic grows in complexity by reading in a huge list of instructions from memory and handing them off to the different execution units that are idle at that point. The results are then collected and re-ordered at the end (Sony VGN-FW11S Battery) .

Out-of-order execution

The addition of caches reduces the frequency or duration of stalls due to waiting for data to be fetched from the memory hierarchy, but does not get rid of these stalls entirely. In early designs a cache miss would force the cache controller to stall the processor and wait (Sony VGN-FW11M Battery) .

Of course there may be some other instruction in the program whose data is available in the cache at that point. Out-of-order execution allows that ready instruction to be processed while an older instruction waits on the cache, then re-orders the results to make it appear that everything happened in the programmed order (Sony VGN-FW139E/H battery) .

This technique is also used to avoid other operand dependency stalls, such as an instruction awaiting a result from a long latency floating-point operation or other multi-cycle operations.

Register renaming

Register renaming refers to a technique used to avoid unnecessary serialized execution of program instructions because of the reuse of the same registers by those instructions (Dell Latitude E5400 Battery) .

Suppose we have two groups of instruction that will use the same register, one set of instruction is executed first to leave the register to the other set, but if the other set is assigned to a different similar register both sets of instructions can be executed in parallel (Dell Latitude E4200 Battery) .

Multiprocessing and multithreading

Computer architects have become stymied by the growing mismatch in CPU operating frequencies and DRAM access times. None of the techniques that exploited instruction-level parallelism within one program could make up for the long stalls that occurred when data had to be fetched from main memory (Dell Vostro A840 Battery) .

Additionally, the large transistor counts and high operating frequencies needed for the more advanced ILP techniques required power dissipation levels that could no longer be cheaply cooled. For these reasons, newer generations of computers have started to exploit higher levels of parallelism that exist outside of a single program or program thread (Dell Inspiron 300M Battery) .

This trend is sometimes known as throughput computing. This idea originated in the mainframe market where online transaction processing emphasized not just the execution speed of one transaction, but the capacity to deal with massive numbers of transactions (Dell Studio 1737 battery) .

With transaction-based applications such as network routing and web-site serving greatly increasing in the last decade, the computer industry has re-emphasized capacity and throughput issues.

One technique of how this parallelism is achieved is through multiprocessing systems, computer systems with multiple CPUs (Dell Inspiron E1505 battery) .

Once reserved for high-end mainframes and supercomputers, small scale (2-8) multiprocessors servers have become commonplace for the small business market. For large corporations, large scale (16-256) multiprocessors are common. Even personal computers with multiple CPUs have appeared since the 1990s (Dell RM791 battery) .

With further transistor size reductions made available with semiconductor technology advances, multicore CPUs have appeared where multiple CPUs are implemented on the same silicon chip. Initially used in chips targeting embedded markets, where simpler and smaller CPUs would allow multiple instantiations to fit on one piece of silicon (Dell XPS M1530 battery) .

By 2005, semiconductor technology allowed dual high-end desktop CPUs CMP chips to be manufactured in volume. Some designs, such as Sun Microsystems' UltraSPARC T1 have reverted back to simpler (scalar, in-order) designs in order to fit more processors on one piece of silicon (Dell XPS M2010 battery) .

Another technique that has become more popular recently is multithreading. In multithreading, when the processor has to fetch data from slow system memory, instead of stalling for the data to arrive, the processor switches to another program or program thread which is ready to execute (Dell Vostro 1000 battery) .

Though this does not speed up a particular program/thread, it increases the overall system throughput by reducing the time the CPU is idle.

Conceptually, multithreading is equivalent to a context switch at the operating system level (Acer Aspire One battery) .

The difference is that a multithreaded CPU can do a thread switch in one CPU cycle instead of the hundreds or thousands of CPU cycles a context switch normally requires. This is achieved by replicating the state hardware (such as the register file and program counter) for each active thread (Toshiba Satellite P10 Battery) .

A further enhancement is simultaneous multithreading. This technique allows superscalar CPUs to execute instructions from different programs/threads simultaneously in the same cycle (SONY VGN-FZ210CE Battery) .

A microprocessor incorporates most or all of the functions of a computer's central processing unit (CPU) on a single integrated circuit (IC, or microchip).The first microprocessors emerged in the early 1970s and were used for electronic calculators, using binary-coded decimal (BCD) arithmetic on 4-bit words (Dell Precision M70 Battery) .

Other embedded uses of 4-bit and 8-bit microprocessors, such as terminals, printers, various kinds of automation etc., followed soon after. Affordable 8-bit microprocessors with 16-bit addressing also led to the first general-purpose microcomputers from the mid-1970s on (Toshiba Satellite L305 Battery) .

During the 1960s, computer processors were often constructed out of small and medium-scale ICs containing from tens to a few hundred transistors. The integration of a whole CPU onto a single chip greatly reduced the cost of processing power (Toshiba Satellite T4900 Battery) .

From these humble beginnings, continued increases in microprocessor capacity have rendered other forms of computers almost completely obsolete (see history of computing hardware), with one or more microprocessors used in everything from the smallest embedded systems and handheld devices to the largest mainframes and supercomputers (Toshiba PA3399U-2BRS battery) .

Since the early 1970s, the increase in capacity of microprocessors has been a consequence of Moore's Law, which suggests that the number of transistors that can be fitted onto a chip doubles every two years. Although originally calculated as a doubling every year,Moore later refined the period to two years (Toshiba Satellite A200 Battery) .

It is often incorrectly quoted as a doubling of transistors every 18 months.

Firsts

Three projects delivered a microprocessor at about the same time: Intel's 4004, Texas Instruments (TI) TMS 1000, and Garrett AiResearch's Central Air Data Computer (CADC) (Toshiba Satellite 1200 Battery) .

Intel 4004

The Intel 4004 is generally regarded as the first microprocessor, and cost thousands of dollars. The first known advertisement for the 4004 is dated November 1971 and appeared in Electronic News.The project that produced the 4004 originated in 1969, when Busicom, a Japanese calculator manufacturer, asked Intel to build a chipset for high-performance desktop calculators (Toshiba Satellite M300 Battery) .

Busicom's original design called for a programmable chip set consisting of seven different chips. Three of the chips were to make a special-purpose CPU with its program stored in ROM and its data stored in shift register read-write memory WD passport essential (500GB/640GB) .

Ted Hoff, the Intel engineer assigned to evaluate the project, believed the Busicom design could be simplified by using dynamic RAM storage for data, rather than shift register memory, and a more traditional general-purpose CPU architecture. Hoff came up with a four–chip architectural proposal WD passport essential (250GB/320GB) :

a ROM chip for storing the programs, a dynamic RAM chip for storing data, a simple I/O device and a 4-bit central processing unit (CPU). Although not a chip designer, he felt the CPU could be integrated into a single chip. This chip would later be called the 4004 microprocessor WD passport essential SE (750GB/1TB) .

The architecture and specifications of the 4004 came from the interaction of Hoff with Stanley Mazor, a software engineer reporting to him, and with Busicom engineer Masatoshi Shima, during 1969. In April 1970, Intel hired Federico Faggin to lead the design of the four-chip set WD passport elite(250GB/320GB) .

Faggin, who originally developed the silicon gate technology (SGT) in 1968 at Fairchild Semiconductor and designed the world’s first commercial integrated circuit using SGT, the Fairchild 3708, had the correct background to lead the project since it was SGT that made it possible to implement a single-chip CPU with the proper speed, power dissipation and cost WD passport elite(500GB/640GB) .

Faggin also developed the new methodology for random logic design, based on silicon gate, that made the 4004 possible. Production units of the 4004 were first delivered to Busicom in March 1971 and shipped to other customers in late 1971 WD passport studio for Mac(320GB/500GB) .

TMS 1000

The Smithsonian Institution says TI engineers Gary Boone and Michael Cochran succeeded in creating the first microcontroller (also called a microcomputer) in 1971. The result of their work was the TMS 1000, which went commercial in 1974.

TI developed the 4-bit TMS 1000 and stressed pre-programmed embedded applications, introducing a version called the TMS1802NC on September 17, 1971 which implemented a calculator on a chip WD passport studio for Mac(500GB/640GB) .

TI filed for the patent on the microprocessor. Gary Boone was awarded U.S. Patent 3,757,306 for the single-chip microprocessor architecture on September 4, 1973. It may never be known which company actually had the first working microprocessor running on the lab bench WD Elements series(250GB/320GB) .

In both 1971 and 1976, Intel and TI entered into broad patent cross-licensing agreements, with Intel paying royalties to TI for the microprocessor patent. A nice history of these events is contained in court documentation from a legal dispute between Cyrix and Intel, with TI as intervenor and owner of the microprocessor patent WD Elements SE(500GB/640GB) .

A computer-on-a-chip is a variation of a microprocessor that combines the microprocessor core (CPU), some program memory and read/write memory, and I/O (input/output) lines onto one chip. The computer-on-a-chip patent, called the "microcomputer patent" at the time, U.S WD Elements SE(750GB/1TB) .

Patent 4,074,351, was awarded to Gary Boone and Michael J. Cochran of TI. Aside from this patent, the standard meaning of microcomputer is a computer using one or more microprocessors as its CPU(s), while the concept defined in the patent is more akin to a microcontroller WD Elements desktop(500GB/640GB) .

Pico/General Instrument

In 1971 Pico Electronics and General Instrument (GI) introduced their first collaboration in ICs, a complete single chip calculator IC for the Monroe/Litton Royal Digital III calculator WD Elements desktop(750GB/1TB) .

This chip could also arguably lay claim to be one of the first microprocessors or microcontrollers having ROM, RAM and a RISC instruction set on-chip. The layout for the four layers of the PMOS process was hand drawn at x500 scale on mylar film, a significant task at the time given the complexity of the chip WD Elements desktop(1.5 TB/2TB) .

Pico was a spinout by five GI design engineers whose vision was to create single chip calculator ICs. They had significant previous design experience on multiple calculator chipsets with both GI and Marconi-Elliott. The key team members had originally been tasked by Elliott Automation to create an 8 bit computer in MOS and had helped establish a MOS Research Laboratory in Glenrothes, Scotland in 1967 WD passport essential SE (750GB/1TB)--USB 3.0) .

Calculators were becoming the largest single market for semiconductors and Pico and GI went on to have significant success in this burgeoning market. GI continued to innovate in microprocessors and microcontrollers with products including the PIC1600, PIC1640 and PIC1650 WD passport essential (500GB/640GB) .

In 1987 the GI Microelectronics business was spun out into the very successful PIC microcontroller business.

CADC

In 1968, Garrett AiResearch (which employed designers Ray Holt and Steve Geller) was invited to produce a digital computer to compete withelectromechanical systems then under development for the main flight control computer in the US Navy's new F-14 Tomcat fighter WD passport for Mac(320GB/500GB) .

The design was complete by 1970, and used a MOS-based chipset as the core CPU. The design was significantly (approximately 20 times) smaller and much more reliable than the mechanical systems it competed against, and was used in all of the early Tomcat models WD passport for Mac(640GB/1TB) .

This system contained "a 20-bit, pipelined, parallel multi-microprocessor". The Navy refused to allow publication of the design until 1997. For this reason the CADC, and the MP944 chipset it used, are fairly unknown. Ray Holt graduated California Polytechnic University in 1968, and began his computer design career with the CADC My book essential 4 generation (640GB/1TB) .

From its inception, it was shrouded in secrecy until 1998 when at Holt's request, the US Navy allowed the documents into the public domain. Since then several have debated if this was the first microprocessor. Holt has stated that no one has compared this microprocessor with those that came later WD My book essential 4 generation( 1.5TB/2TB) .

According to Parab et al. (2007), "The scientific papers and literature published around 1971 reveal that the MP944 digital processor used for the F-14 Tomcat aircraft of the US Navy qualifies as the first microprocessor. Although interesting, it was not a single-chip processor, and was not general purpose – it was more like a set of parallel building blocks you could use to make a special-purpose DSP form WD My book elite( 1TB/1.5TB) .

It indicates that today’s industry theme of converging DSP-microcontroller architectures was started in 1971." This convergence of DSP and microcontroller architectures is known as a Digital Signal Controller.

Gilbert Hyatt

Gilbert Hyatt was awarded a patent claiming an invention pre-dating both TI and Intel, describing a "microcontroller" WD My book studio(1TB/2TB) .

The patent was later invalidated, but not before substantial royalties were paid out.

Four-Phase Systems AL1

The Four-Phase Systems AL1 was an 8-bit bit slice chip containing eight registers and an ALU.It was designed by Lee Boysel in 1969 WD My book essential 4 generation( 1.5TB/2TB) .

At the time, it formed part of a nine-chip, 24-bit CPU with three AL1s, but it was later called a microprocessor when, in response to 1990s litigation by Texas Instruments, a demonstration system was constructed where a single AL1 formed part of a courtroom demonstration computer system, together with RAM, ROM, and an input-output device WD My book elite(640GB/2TB) .

8-bit designs

The Intel 4004 was followed in 1972 by the Intel 8008, the world's first 8-bit microprocessor. According to A History of Modern Computing, (MIT Press), pp. 220–21, Intel entered into a contract with Computer Terminals Corporation, later called Datapoint, of San Antonio TX, for a chip for a terminal they were designing Seagate expansion portable (750GB/1TB) .

Datapoint later decided not to use the chip, and Intel marketed it as the 8008 in April, 1972. This was the world's first 8-bit microprocessor. It was the basis for the famous "Mark-8" computer kit advertised in the magazine Radio-Electronics in 1974.

The 8008 was the precursor to the very successful Intel 8080 (1974), Zilog Z80 (1976), and derivative Intel 8-bit processors Seagate expansion portable (320GB/500GB) .

The competing Motorola 6800 was released August 1974 and the similarMOS Technology 6502 in 1975 (designed largely by the same people). The 6502 rivaled the Z80 in popularity during the 1980s.

A low overall cost, small packaging, simple computer bus requirements, and sometimes the integration of extra circuitry (e.g. the Z80's built-in memory refresh circuitry) allowed the home computer"revolution" to accelerate sharply in the early 1980s Seagate expansion (1.5TB/2TB) .

This delivered such inexpensive machines as the Sinclair ZX-81, which sold for US$99.

The Western Design Center, Inc. (WDC) introduced the CMOS 65C02 in 1982 and licensed the design to several firms. It was used as the CPU in the Apple IIe and IIc personal computers as well as in medical implantable grade pacemakers and defibrilators, automotive, industrial and consumer devices Seagate Freeagent Desktop (500GB/1TB) .

WDC pioneered the licensing of microprocessor designs, later followed by ARM and other microprocessor Intellectual Property (IP) providers in the 1990s.

Motorola introduced the MC6809 in 1978, an ambitious and thought-through 8-bit design source compatible with the 6800 and implemented using purely hard-wired logic Seagate Freeagent Go(250GB/320GB) .

(Subsequent 16-bit microprocessors typically used microcode to some extent, as CISC design requirements were getting too complex for purely hard-wired logic only.)

Another early 8-bit microprocessor was the Signetics 2650, which enjoyed a brief surge of interest due to its innovative and powerful instruction set architecture Seagate Freeagent Go(500GB/640GB) .

A seminal microprocessor in the world of spaceflight was RCA's RCA 1802 (aka CDP1802, RCA COSMAC) (introduced in 1976), which was used onboard the Galileo probe to Jupiter (launched 1989, arrived 1995). RCA COSMAC was the first to implement CMOS technology Seagate Freeagent Go(750GB/1TB) .

The CDP1802 was used because it could be run at very low power, and because a variant was available fabricated using a special production process (Silicon on Sapphire), providing much better protection against cosmic radiation and electrostatic discharges than that of any other processor of the era Seagate Freeagent Goflex(250GB/320GB) .

Thus, the SOS version of the 1802 was said to be the first radiation-hardened microprocessor.

The RCA 1802 had what is called a static design, meaning that the clock frequency could be made arbitrarily low, even to 0 Hz, a total stop condition Seagate Freeagent Goflex(500GB/640GB) .

This let the Galileo spacecraft use minimum electric power for long uneventful stretches of a voyage. Timers and/or sensors would awaken/improve the performance of the processor in time for important tasks, such as navigation updates, attitude control, data acquisition, and radio communication Seagate Freeagent Goflex(750GB/1TB) .

12-bit designs

The Intersil 6100 family consisted of a 12-bit microprocessor (the 6100) and a range of peripheral support and memory ICs. The microprocessor recognised the DEC PDP-8 minicomputer instruction set. As such it was sometimes referred to as the CMOS-PDP8Seagate Freeagent Goflex Pro(500GB/750GB) .

Since it was also produced by Harris Corporation, it was also known as the Harris HM-6100. By virtue of its CMOS technology and associated benefits, the 6100 was being incorporated into some military designs until the early 1980s.

16-bit designs

The first multi-chip 16-bit microprocessor was the National Semiconductor IMP-16, introduced in early 1973 Seagate Freeagent Goflex desktop(1TB/2TB) .

An 8-bit version of the chipset was introduced in 1974 as the IMP-8.

Other early multi-chip 16-bit microprocessors include one used by Digital Equipment Corporation (DEC) in the LSI-11 OEM board set and the packaged PDP 11/03 minicomputer, and the Fairchild Semiconductor MicroFlame 9440, both of which were introduced in the 1975 to 1976 timeframe Seagate Freeagent go for Mac(320GB/640GB) .

In 1975, National introduced the first 16-bit single-chip microprocessor, the National Semiconductor PACE, which was later followed by an NMOS version, the INS8900.

Another early single-chip 16-bit microprocessor was TI's TMS 9900, which was also compatible with their TI-990 line of minicomputers Samsung G2 protable (250gb/320GB) .

The 9900 was used in the TI 990/4 minicomputer, the TI-99/4Ahome computer, and the TM990 line of OEM microcomputer boards. The chip was packaged in a large ceramic 64-pin DIP package, while most 8-bit microprocessors such as the Intel 8080 used the more common, smaller, and less expensive plastic 40-pin DIP Samsung G2 protable (500GB/640GB) .

A follow-on chip, the TMS 9980, was designed to compete with the Intel 8080, had the full TI 990 16-bit instruction set, used a plastic 40-pin package, moved data 8 bits at a time, but could only address 16 KB. A third chip, the TMS 9995, was a new design. The family later expanded to include the 99105 and 99110 Samsung S2 protable (320GB/500GB) .

The Western Design Center, Inc. (WDC) introduced the CMOS 65816 16-bit upgrade of the WDC CMOS 65C02 in 1984. The 65816 16-bit microprocessor was the core of the Apple IIgs and later theSuper Nintendo Entertainment System, making it one of the most popular 16-bit designs of all time Samsung S1 Mini (120GB/160GB) .

Intel followed a different path, having no minicomputers to emulate, and instead "upsized" their 8080 design into the 16-bit Intel 8086, the first member of the x86 family, which powers most modern PCtype computers. Intel introduced the 8086 as a cost effective way of porting software from the 8080 lines, and succeeded in winning much business on that premise Samsung S1 Mini (250GB/320GB) .

The 8088, a version of the 8086 that used an external 8-bit data bus, was the microprocessor in the first IBM PC, the model 5150. Following up their 8086 and 8088, Intel released the 80186, 80286 and, in 1985, the 32-bit 80386, cementing their PC market dominance with the processor family's backwards compatibility Samsung story station (1TB/1.5TB) .

The 8086 and 80186 had a crude method of segmentation, while the 80286 introduced a full-featured semgented memory management unit (MMU), and the 80386 introduced a flat 32-bit memory model with paged memory management Samsung Story station (1.5TB/2TB) .

32-bit designs

The most significant of the 32-bit designs is the MC68000, introduced in 1979. The 68K, as it was widely known, had 32-bit registers but used 16-bit internal data paths and a 16-bit external data bus to reduce pin count, and supported only 24-bit addresses Samsung story station Esata(1TB/1.5TB) .

Motorola generally described it as a 16-bit processor, though it clearly has 32-bit architecture. The combination of high performance, large (16 megabytes or 224 bytes) memory space and fairly low cost made it the most popular CPU design of its class. The Apple Lisa and Macintosh designs made use of the 68000, as did a host of other designs in the mid-1980s, including the Atari ST and Commodore Amiga Samsung G3 station (1TB/1.5TB) .

The world's first single-chip fully-32-bit microprocessor, with 32-bit data paths, 32-bit buses, and 32-bit addresses, was the AT&T Bell Labs BELLMAC-32A, with first samples in 1980, and general production in 1982 After the divestiture of AT&T in 1984, it was renamed the WE 32000 (WE for Western Electric), and had two follow-on generations, the WE 32100 and WE 32200 Maxtor one touch 4 plus (500GB/750GB) .

These microprocessors were used in the AT&T 3B5 and 3B15 minicomputers; in the 3B2, the world's first desktop supermicrocomputer; in the "Companion", the world's first 32-bit laptop computer; and in "Alexander", the world's first book-sized supermicrocomputer, featuring ROM-pack memory cartridges similar to today's gaming consoles Maxtor one touch 4 plus (1TB/1.5TB) .

All these systems ran the UNIX System V operating system.

Intel's first 32-bit microprocessor was the iAPX 432, which was introduced in 1981 but was not a commercial success. It had an advanced capability-basedobject-oriented architecture, but poor performance compared to contemporary architectures such as Intel's own 80286 (introduced 1982), which was almost four times as fast on typical benchmark tests Maxtor black diamond (320GB/500GB) .

However, the results for the iAPX432 was partly due to a rushed and therefore suboptimal Ada compiler.

The ARM first appeared in 1985. This is a RISC processor design, which has since come to dominate the 32-bit embedded systems processor space due in large part to its power efficiency, its licensing model, and its wide selection of system development tools Maxtor cool black(640GB/1TB) .

Semiconductor manufacturers generally license cores such as the ARM11 and integrate them into their own system on a chipproducts; only a few such vendors are licensed to modify the ARM cores. Most cell phones include an ARM processor, as do a wide variety of other products Maxtor Black diamond (320GB/500GB) .

There are microcontroller-oriented ARM cores without virtual memory support, as well as SMP applications processors with virtual memory.

Motorola's success with the 68000 led to the MC68010, which added virtual memory support. The MC68020, introduced in 1985 added full 32-bit data and address busses. The 68020 became hugely popular in the Unix supermicrocomputer market, and many small companies (e.g., Altos, Charles River Data Systems) produced desktop-size systems Hitachi simple touch (250GB/320GB) .

The MC68030 was introduced next, improving upon the previous design by integrating the MMU into the chip. The continued success led to the MC68040, which included an FPU for better math performance. A 68050 failed to achieve its performance goals and was not released, and the follow-up MC68060 was released into a market saturated by much faster RISC designs Hitachi simple touch (320GB/500GB) .

The 68K family faded from the desktop in the early 1990s.

Other large companies designed the 68020 and follow-ons into embedded equipment. At one point, there were more 68020s in embedded equipment than there were Intel Pentiums in PCs.TheColdFire processor cores are derivatives of the venerable 68020 Hitachi life studio (320GB/500GB) .

During this time (early to mid-1980s), National Semiconductor introduced a very similar 16-bit pinout, 32-bit internal microprocessor called the NS 16032 (later renamed 32016), the full 32-bit version named the NS 32032. Later the NS 32132 was introduced which allowed two CPUs to reside on the same memory bus, with built in arbitration Hitachi life studio (250GB/320GB).

The NS32016/32 outperformed the MC68000/10 but the NS32332 which arrived at approximately the same time the MC68020 did not have enough performance. The third generation chip, the NS32532 was different. It had about double the performance of the MC68030 which was released around the same time Hitachi life studio platinum (250GB/320GB) .

The appearance of RISC processors like the AM29000 and MC88000 (now both dead) influenced the architecture of the final core, the NS32764. Technically advanced, using a superscalar RISC core, internally overclocked, with a 64 bit bus, it was still capable of executing Series 32000 instructions through real time translation Hitachi life studio platinum (320GB/500GB) .

When National Semiconductor decided to leave the Unix market, the chip was redesigned into the Swordfish Embedded processor with a set of on chip peripherals. The chip turned out to be too expensive for the laser printer market and was killed Hitachi life studio desk (500GB/1TB) .

The design team went to Intel and there designed the Pentium processor which is very similar to the NS32764 core internally The big success of the Series 32000 was in the laser printer market, where the NS32CG16 with microcoded BitBlt instructions had very good price/performance and was adopted by large companies like Canon Hitachi life studio plus (320GB/500GB) .

By the mid-1980s, Sequent introduced the first symmetric multiprocessor (SMP) server-class computer using the NS 32032. This was one of the design's few wins, and it disappeared in the late 1980s. TheMIPS R2000 (1984) and R3000 (1989) were highly successful 32-bit RISC microprocessors Hitachi life studio plus (320GB/500GB) .

They were used in high-end workstations and servers by SGI, among others. Other designs included the interesting Zilog Z80000, which arrived too late to market to stand a chance and disappeared quickly.

In the late 1980s, "microprocessor wars" started killing off some of the microprocessors Hitachi X mobile (250GB/320GB) .

Apparently, with only one major design win, Sequent, the NS 32032 just faded out of existence, and Sequent switched to Intel microprocessors.

From 1985 to 2003, the 32-bit x86 architectures became increasingly dominant in desktop, laptop, and server markets, and these microprocessors became faster and more capable Hitachi X mobile(320GB/500GB) .

Intel had licensed early versions of the architecture to other companies, but declined to license the Pentium, so AMD and Cyrix built later versions of the architecture based on their own designs. During this span, these processors increased in complexity (transistor count) and capability (instructions/second) by at least three orders of magnitude Hitachi XL (1TB/2TB) .

Intel's Pentium line is probably the most famous and recognizable 32-bit processor model, at least with the public at large.

64-bit designs in personal computers

While 64-bit microprocessor designs have been in use in several markets since the early 1990s, the early 2000s saw the introduction of 64-bit microprocessors targeted at the PC market Toshiba canvio portable(320GB/500GB) .

With AMD's introduction of a 64-bit architecture backwards-compatible with x86, x86-64 (also called AMD64), in September 2003, followed by Intel's near fully compatible 64-bit extensions (first called IA-32e or EM64T, later renamed Intel 64), the 64-bit desktop era began Toshiba canvio portable(750GB/1TB) .

Both versions can run 32-bit legacy applications without any performance penalty as well as new 64-bit software. With operating systems Windows XP x64, Windows Vista x64, Windows 7 x64, Linux, BSD and Mac OS X that run 64-bit native, the software is also geared to fully utilize the capabilities of such processors Toshiba anvio for Mac(500GB/750GB) .

The move to 64 bits is more than just an increase in register size from the IA-32 as it also doubles the number of general-purpose registers.

The move to 64 bits by PowerPC processors had been intended since the processors' design in the early 90s and was not a major cause of incompatibility Toshiba canvio for Mac(750GB/1TB) .

Existing integer registers are extended as are all related data pathways, but, as was the case with IA-32, both floating point and vector units had been operating at or above 64 bits for several years. Unlike what happened when IA-32 was extended to x86-64, no new general purpose registers were added in 64-bit PowerPC, so any performance gained when using the 64-bit mode for applications making no use of the larger address space is minimal Toshiba External HDD –portable(320GB/500GB) .

Multicore designs

A different approach to improving a computer's performance is to add extra processors, as in symmetric multiprocessing designs, which have been popular in servers and workstations since the early 1990s. Keeping up with Moore's Law is becoming increasingly challenging as chip-making technologies approach the physical limits of the technology Toshiba portable(500GB/640GB) .