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
binary-coded decimal (BCD) arithmetic
on 4-bit
words. Other
embedded uses of 4- and 8-bit
microprocessors, such as
terminal,
printer, 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.
Computer 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
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
mainframe and
supercomputers.
Since the early 1970s, the increase in capacity of microprocessors
has been known to generally follow
Moore's
Law, which suggests that the complexity of an integrated
circuit, with respect to minimum component cost, doubles every two
years.In the late 1990s, and in the high-performance microprocessor
segment, heat generation (
TDP),
due to switching losses, static 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). Intel's 4004 is considered the first microprocesor,
and cost in the thousands of dollars. The first known advertisement
for the 4004 is dated to November 1971; it 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. Busicom original design
called for a programmable chip set consisting of 7 different chips,
three of them were used to make a special-purpose CPU with its
program stored in ROM and its data stored in shift register
read-write memory.
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: 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), which he felt could be integrated
into a single chip, although he was not a chip designer. This chip
would later be called the 4004 microprocessor. The architecture and
specifications of the 4004 were the results of the interaction of
Intel’s Hoff with
Stanley Mazor, a
software engineer reporting to Hoff, and with Busicom engineer
Masatoshi Shima. In April 1970 Intel
hired
Federico Faggin to lead the
design of the four-chip set. Faggin, who originally developed the
silicon gate technology (SGT) in 1968 at Fairchild Semiconductor
[2924] (and also designed the world’s first commercial
integrated circuit using SGT – the Fairchild 3708), had the correct
background to lead the project since it was the SGT to make
possible the design of a CPU into a single chip with the proper
speed, power dissipation and cost. 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.
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.
In early 1971
Pico Electronics. and
General Instrument introduced
their first collaboration in ICs, a complete single chip calculator
IC for the Monroe Royal Digital III calculator. This IC could also
arguably lay claim to be one of the first microprocessors or
microcontrollers having ROM, RAM and a
RISC
instruction set on-chip. 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. Pico and GI went on to
have significant success in the burgeoning handheld calculator
market.
The design engineer Ray Holt, a graduate of California
Polytechnical University in 1968, began his computer design career
with the F14 CADC. The central air data computer was shrouded in
secrecy for over 30 years from its creation (the year being 1968),
it was not publicly known until 1998 at which time, at the request
of Mr. Ray Holt, the US Navy allowed the documents into the public
domain. Since then many debates have argued that this was, in fact,
the first microprocessor. 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. It indicates that today’s industry theme of converging
DSP-microcontroller architectureswas started in 1971. This
convergence of DSP and microcontroller architectures is known as a
Digital Signal
Controller.
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 who led
the design of the 4004 in 1970-1971, and
Ted
Hoff who led the architecture in 1969. The head of the MOS
Department 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
intervenor 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.It is also called as
micro-controller. 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
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 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 and the
similar
MOS 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
circuitry otherwise provided by external hardware (the Z80 had a
built in
memory refresh) 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 was used as the
CPU in the
Apple IIc and IIe personal
computers as well as in medical implantable grade pacemakers and
defibrilators, automotive, industrial and consumer devices. WDC
pioneered the licensing of microprocessor designs, later followed
by
ARM and other microprocessor
Intellectual Property (IP)
providers in the 1990’s.
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. (Subsequent 16-bit
microprocessors typically used
microcode
to some extent, as 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. 8086
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/improve
the performance of 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 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 had only been on the market briefly when 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
performance, large (16
megabytes or
2
24 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.
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
was not a commercial success. It had an advanced
capability-based object-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. However, the results for the
iAPX432 was partly due to a rushed and therefore suboptimal
Ada compiler.
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. 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. 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 three orders of magnitude.
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.
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 near 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 performance penalty as well as new 64-bit
software. With operating systems
Windows XP x64,
Windows Vista 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. 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. 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.
Multicore designs

Pentium D dual core processors
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 rates
compared to discrete multiprocessor systems, improving overall
system performance.
In 2005, the first personal computer dual-core processors were
announced and as of 2009 dual-core and quad-core processors are
widely used in servers, workstations and PCs while six and
eight-core processors will be 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.
High-end Intel Xeon processors that are on the LGA771 socket are DP
(dual processor) capable, as well as the Intel Core 2 Extreme
QX9775 also used in the Mac Pro by Apple and the Intel Skulltrail
motherboard. With the transition to the LGA1366 socket and the
Intel i7 chip quad core is now considered mainstream and the
upcoming i9 chip will introduce six and possibly dual-die hex-core
(12-cores), processors.
RISC
In the mid-1980s to early-1990s, a crop of new high-performance
Reduced Instruction Set Computer (
RISC)
microprocessors appeared, influenced by discrete RISC-like CPU
designs such as the
IBM 801 and others. RISC
microprocessors were initially used in special-purpose machines and
Unix workstations,
but then gained wide acceptance in other roles.
In 1986, HP released its first system with a
PA-RISC CPU.
The first commercial microprocessor design
was released either by MIPS Computer Systems
, the 32-bit R2000 (the R1000 was not released) or
by Acorn computers, the 32-bit
ARM2 in 1987. The R3000 made
the design truly practical, and the
R4000
introduced the world's first commercially available 64-bit RISC
microprocessor. Competing projects would result in the IBM
POWER and
Sun
SPARC architectures. 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.
As of 2007, two 64-bit RISC architectures are still produced in
volume for non-embedded applications:
SPARC
and
Power ISA.
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 is 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. 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.
About 55% of all
CPU sold in
the world are
8-bit microcontrollers, over two billion of which
were sold in 1997.
As of 2002, 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. Most
microprocessors are used in embedded control applications such as
household appliances, automobiles, and computer peripherals. Taken
as a whole, the average price for a microprocessor,
microcontroller, or
DSP is
just over $6.
About ten billion CPUs were manufactured in 2008.About 98% of new
CPUs produced each year are embedded.
Architectures
See also
Major designers
In 2007, the companies with the largest share of the microprocessor
controller market were
Other microprocessor design companies include:
An abundance of market research has (and still does) contradict the
above list of "major designers". See and and just to name a few.
Together Intel and AMD usually account for about 90% of the
MICROPROCESSOR market. The above "LaPedus" article is about the
MICROCONTROLLER market.
Notes
References
- Ak Ray & KM Bhurchandi , "Advanced Microprocessors and
Peripherals on Architecture Programming and Interfacing"
published in India by Tata McGraw Hill Publishing Company Ltd.
External links
General
Historical documents