Everything about Microprocessor totally explained
A
microprocessor incorporates most or all of the functions of a
central processing unit (CPU) on a single
integrated circuit (IC). The first microprocessors emerged in the early 1970s and were used for electronic
calculators, using
BCD arithmetics on 4-bit
words. Other
embedded uses of 4 and 8-bit microprocessors, such as
terminals,
printers, various kinds of
automation etc, followed rather quickly. Affordable 8-bit microprocessors with 16-bit addressing also led to
the first general purpose
microcomputers in the mid-1970s.
Processors were for a long period constructed out of small and medium-scale ICs containing the equivalent of a few to a few hundred transistors. The integration of the whole CPU onto a single
VLSI chip therefore greatly reduced the cost of processing capacity. From their 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 microprocessor as processing element in everything from the smallest
embedded systems and
handheld devices to the largest
mainframes and
supercomputers.
Since the early 1970s, the increase in processing capacity of evolving microprocessors has been known to generally follow
Moore's Law. It suggests that the complexity of an integrated circuit, with respect to minimum component cost, doubles every 18 months. In the late 1990s, heat generation (
TDP), due to current leakage and other factors, emerged as a leading developmental constraint.
History
First types
Three projects arguably delivered a complete microprocessor at about the same time, namely
Intel's
4004, the
Texas Instruments (TI)
TMS 1000, and
Garrett AiResearch's
Central Air Data Computer (CADC).
In 1968, Garrett AiResearch, with designer
Ray Holt and Steve Geller, were invited to produce a digital computer to compete with
electromechanical systems then under development for the main flight control computer in the
US Navy's new
F-14 Tomcat fighter. 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. This system contained a "a 20-bit, pipelined, parallel multi-microprocessor". However, the system was considered so advanced that 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 even today.
(see First Microprocessor Chip Set.)
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. The Intel chip was the 4-bit
4004, released on
November 15,
1971, developed by
Federico Faggin and
Marcian Hoff, the manager of the designing team was
Leslie L. Vadász.
TI filed for the patent on the microprocessor. Gary Boone was awarded 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. 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 and owner of the microprocessor patent.
Interestingly, a third party (Gilbert Hyatt) was awarded a patent which might cover the "microprocessor". See
a webpage claiming an invention pre-dating both TI and Intel, describing a "microcontroller". According to
a rebuttal and
a commentary, the patent was later invalidated, but not before substantial royalties were paid out.
A computer-on-a-chip is a variation of a microprocessor which combines the microprocessor core (CPU), some memory, and I/O (
input/output) lines, all on one
chip. The computer-on-a-chip patent, called the "microcomputer patent" at the time,, 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 perhaps more akin to a
microcontroller.
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. Datapoint later decided 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 and its successor, the world-famous 8080, opened up the microprocessor component marketplace.
Notable 8-bit designs
The 4004 was later followed in 1972 by the
8008, the world's first
8-bit microprocessor.
These processors are the precursors to the very successful
Intel 8080 (1974),
Zilog Z80 (1976), and derivative Intel 8-bit processors.
The competing
Motorola 6800 was released August 1974. Its architecture was cloned and improved in the
MOS Technology 6502 in 1975, rivaling the Z80 in popularity during the 1980s.
Both the Z80 and 6502 concentrated on low overall cost, by combining small packaging, simple
computer bus requirements, and including circuitry that normally must be provided in a separate chip (example: the Z80 included a memory controller). It was these features that allowed the
home computer "revolution" to accelerate sharply in the early 1980s, eventually delivering 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 became the core of the
Apple IIc and IIe personal computers, medical implantable grade pacemakers and defibrilators, automotive, industrial and consumer devices. WDC pioneered the licensing of microprocessor technology which was later followed by
ARM and other microprocessor
Intellectual Property (IP) providers in the 1990’s.
Motorola trumped the entire 8-bit market by introducing the
MC6809 in 1978, arguably one of the most powerful,
orthogonal, and clean 8-bit microprocessor designs ever fielded – and also one of the most complex hard-wired logic designs that ever made it into production for any microprocessor.
Microcoding replaced hardwired logic at about this time for all designs more powerful than the MC6809 – because the design requirements were getting too complex for hardwired logic.
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.
A seminal microprocessor in the world of spaceflight was
RCA's
RCA 1802 (aka CDP1802, RCA COSMAC) (introduced in 1976) which was used in NASA's
Voyager and
Viking spaceprobes of the 1970s, and onboard the
Galileo probe to Jupiter (launched 1989, arrived 1995). RCA COSMAC was the first to implement C-MOS technology. The CDP1802 was used because it could be run at very
low power, and because its production process (
Silicon on Sapphire) ensured much better protection against
cosmic radiation and
electrostatic discharges than that of any other processor of the era. Thus, the 1802 is 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. This let the
Voyager/
Viking/
Galileo spacecraft use minimum electric power for long uneventful stretches of a voyage. Timers and/or sensors would awaken/speed up the processor in time for important tasks, such as navigation updates, attitude control, data acquisition, and radio communication.
16-bit designs
The first multi-chip
16-bit microprocessor was the
National Semiconductor IMP-16,
introduced in early 1973. An 8-bit version of the chipset was introduced in 1974 as the IMP-8. During the same year, National introduced the first 16-bit single-chip microprocessor, the National Semiconductor PACE, which was later followed by an
NMOS version, the
INS8900.
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.
The first single-chip 16-bit microprocessor was TI's
TMS 9900, which was also compatible with their
TI-990 line of minicomputers. The 9900 was used in the TI 990/4 minicomputer, the
TI-99/4A home 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. 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.
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 the
Super Nintendo Entertainment System, making it one of the most popular 16-bit designs of all time.
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
PC type 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. 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.
The integrated microprocessor
memory management unit (MMU) was developed by Childs et al. of
Intel, and awarded US patent number 4,442,484.
32-bit designs
16-bit designs were in the market only briefly when full 32-bit implementations started to appear.
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. Motorola generally described it as a 16-bit processor, though it clearly has 32-bit
architecture. The combination of high speed, large (16
megabytes (2^24)) memory space and fairly low costs 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.
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 (See this
bibliographic reference and this
general reference). 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. 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. 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 wasn't a commercial success. It had an advanced
capability-based object-oriented architecture, but poor performance compared to other competing architectures such as the Motorola 68000.
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 (for example, Altos, Charles River Data Systems) produced desktop-size systems. Following this with the
MC68030, which added the MMU into the chip, the 68K family became
the processor for everything that wasn't running
DOS. The continued success led to the
MC68040, which included an
FPU for better math performance. A 68050 failed to achieve its performance goals and wasn't released, and the follow-up
MC68060 was released into a market saturated by much faster RISC designs. 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 (See
this webpage for this embedded usage information). The
ColdFire processor cores are derivatives of the venerable 68020.
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, and a line of 32-bit industrial OEM microcomputers. 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.
The
MIPS R2000 (1984) and R3000 (1989) were highly successful 32-bit RISC microprocessors. They were used in high-end workstations and servers by
SGI, among others.
Other designs included the interesting
Zilog Z8000, 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. 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. 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 a factor of 1000. 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 microchips targeted at the PC market.
With AMD's introduction of a 64-bit architecture backwards-compatible with x86,
x86-64 (now called
AMD64), in September 2003, followed by Intel's fully compatible 64-bit extensions (first called IA-32e or EM64T, later renamed
Intel 64), the 64-bit desktop era began. Both versions can run 32-bit legacy applications without any speed penalty as well as new 64-bit software. With operating systems
Windows XP x64,
Windows Vista x64,
Linux and
Mac OS X that run 64-bit native, the software too is geared to utilize the full power of such processors. 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 wasn't a major cause of incompatibility. 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 with 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.
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.
In response, the microprocessor manufacturers look for other ways to improve performance, in order to hold on to the momentum of constant upgrades in the market.
A multi-core processor is simply a single chip containing more than one microprocessor core, effectively multiplying the potential performance with the number of cores (as long as the operating system and software is designed to take advantage of more than one processor). Some components, such as bus interface and second level cache, may be shared between cores. Because the cores are physically very close they interface at much faster clock speeds compared to discrete multiprocessor systems, improving overall system performance.
In 2005, the first mass-market dual-core processors were announced and as of 2007 dual-core processors are widely used in servers, workstations and PCs while quad-core processors are now available for high-end applications in both the home and professional environments.
Sun Microsystems has released the Niagara and Niagara 2 chips, both of which feature an eight-core design. The Niagara 2 supports more threads and operates at 1.6 GHz.
Apple produces the Mac Pro which also utilizes an 8-core
Intel Xeon processor that can operate up to 3.2 GHz.
RISC
In the mid-1980s to early-1990s, a crop of new high-performance
RISC (reduced instruction set computer) microprocessors appeared, which were initially used in special purpose machines and
Unix workstations, but then gained wide acceptance in other roles.
The first commercial design was released by
MIPS Technologies, the 32-bit
R2000 (the R1000 wasn't released). The R3000 made the design truly practical, and the
R4000 introduced the world's first 64-bit design. Competing projects would result in the
IBM POWER and
Sun SPARC systems, respectively. Soon every major vendor was releasing a RISC design, including the
AT&T CRISP,
AMD 29000,
Intel i860 and
Intel i960,
Motorola 88000,
DEC Alpha and the
HP-PA.
Market forces have "weeded out" many of these designs, with almost no desktop or laptop RISC processors and with the SPARC being used in Sun designs only. MIPS is primarily used in embedded systems, notably in
Cisco routers. The rest of the original crop of designs have disappeared. Other companies have attacked niches in the market, notably
ARM, originally intended for home computer use but since focussed on the embedded processor market. Today RISC designs based on the MIPS, ARM or PowerPC core power the vast majority of computing devices.
As of 2007, two 64-bit RISC architectures are still produced in volume:
SPARC and
Power Architecture. The RISC-like
Itanium is produced in smaller quantities. The vast majority of 64-bit microprocessors are now
x86-64 CISC designs from AMD and Intel.
Special-purpose designs
Though the term "microprocessor" has traditionally referred to a single- or multi-chip CPU or
system-on-a-chip (SoC), several types of specialized processing devices have followed from the technology. The most common examples are
microcontrollers,
digital signal processors (DSP) and
graphics processing units (GPU). Many examples of these are either not programmable, or have limited programming facilities. For example, in general GPUs through the 1990s were mostly non-programmable and have only recently gained limited facilities like programmable
vertex shaders. There is no universal consensus on what defines a "microprocessor", but it's usually safe to assume that the term refers to a general-purpose CPU of some sort and not a special-purpose processor unless specifically noted.
Market statistics
In 2003, about $44 billion (USD) worth of microprocessors were manufactured and sold.
(External Link) Although about half of that money was spent on CPUs used in desktop or laptop
personal computers, those count for only about 0.2% of all CPUs sold.
Silicon Valley has an old saying: "The first chip costs a million dollars; the second one costs a nickel." In other words, most of the cost is in the design and the manufacturing setup: once manufacturing is underway, it costs almost nothing.
About 55% of all
CPUs sold in the world are
8-bit microcontrollers. Over 2 billion 8-bit
microcontrollers were sold in 1997.
(External Link)
Less than 10% of all the CPUs sold in the world are
32-bit or more. Of all the 32-bit CPUs sold, about 2% are used in desktop or laptop
personal computers, the rest are sold in household appliances such as toasters, microwaves, vacuum cleaners and televisions.
"Taken as a whole, the average price for a microprocessor,
microcontroller, or
DSP is just over $6."
(External Link)
Architectures
Further Information
Get more info on 'Microprocessor'.
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