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History of Computer 计算机发展史 7 Great Moments in Microprocessor History

 
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Chapter 6
Great Moments in
Microprocessor History

425
6.1 To Beginning
At the dawn of the 19th century, Benjamin
Franklin's discovery of the principles of
electricity were still fairly new, and practical
applications of his discoveries were few -- the
most notable exception being the lightning rod,
which was invented independently by two
different people in two different places.
Independent contemporaneous (and not so
contemporaneous) discovery would remain a
recurring theme in electronics.

426
6.2 Before the Flood: The 1960s
• Just a scant few years after the first laboratory
integrated circuits, Fairchild Semiconductor
introduced the first commercially available integrated
circuit (although at almost the same time as one from
Texas Instruments).
• Already at the start of the decade, process that would
last until the present day was available: commercial
ICs made in the planar process were available from
both Fairchild Semiconductor and Texas Instruments
by 1961, and TTL (transistor-transistor logic) circuits
appeared commercially in 1962. By 1968, CMOS
(complementary metal oxide semiconductor) hit the
market. There is no doubt but that technology, design,
and process were rapidly evolving.

427
• Observing this trend, Fairchild Semiconductor's
director of Research & Development Gordon
Moore observed in 1965 that the density of elements
in ICs was doubling annually, and predicted that
the trend would continue for the next ten years.
With certain amendments, this came to be known as
Moore's Law.
• The first ICs contained just a few transistors per
wafer; by the dawn of the 1970s, production
techniques allowed for thousands of transistors per
wafer. It was only a matter of time before someone
would use this capacity to put an entire computer
on a chip, and several someones, indeed, did just
that.

428
6.3 Development Explosion: The 1970s
The idea of a computer on a single chip
had been described in the literature as
far back as 1952, and more articles like
this began to appear as the 1970s dawned.
Finally, process had caught up to
thinking, and the computer on a chip was
made possible. The air was electric with
the possibility.

429
• Once the feat had been established, the rest of
the decade saw a proliferation of companies old
and new getting into the semiconductor
business, as well as the first personal computers,
the first arcade games, and even the first home
video game systems -- thus spreading consumer
contact with electronics, and paving the way
for continued rapid growth in the 1980s.
• At the beginning of the 1970s, microprocessors
had not yet been introduced. By the end of the
decade, a saturated market led to price wars,
and many processors were already 16-bit.

430
The first three
At the time of this writing, three groups
lay claim for having been the first to put
a computer in a chip: The Central Air
Data Computer (CADC), the Intel® 4004,
and the Texas Instruments TMS 1000.

431
• The CADC system was completed for the Navy's “Tom
Cat” fighter jets in 1970. It is often discounted because
it was a chip set and not a CPU. The TI TMS 1000 was
first to market in calculator form, but not in standalone
form -- that distinction goes to the Intel 4004,
which is just one of the reasons it is often cited as the
first (incidentally, it too was just one in a chipset of
four).
• In truth, it does not matter who was first. As with the
lightning rod, the light bulb, radio -- and so many other
innovations before and after -- it suffices to say it was in
the ether, it was inevitable, its time was come.

432
• CADC spent 20 years in top-secret, cold-war-era
mothballs until finally being declassified in 1998. Thus,
even if it was the first, it has remained under most
people's radar even today, and did not have a chance
to influence other early microprocessor design.
• The Intel 4004 had a short and mostly uneventful
history, to be superseded by the 8008 and other early
Intel chips (see below).
• In 1973, Texas Instrument's Gary Boone was awarded
U.S. Patent No. 3,757,306 for the single-chip
microprocessor architecture. The chip was finally
marketed in stand-alone form in 1974, for the low, low
(bulk) price of US$2 apiece. In 1978, a special version
of the TI TMS 1000 was the brains of the educational
"Speak and Spell" toy which E.T. jerry-rigged to
phone home.

433

434
Early Intel: 4004, 8008, and 8080
Coupled with the fact that the early computers were
difficult to use in the first place, this engendered the
belief that only heroes (and heroines) with size-16
turbo-charged brains had any chance of being
capable of using them at all. Last but not least,
computers of the day required many thousands of
transistors and the thrust was toward yet more
powerful computers in terms of raw numbercrunching
capability, but integrated circuit
technology was in its infancy and it wasn't possible
to construct even a few thousand transistors on a
single integrated circuit until the late 1960s.

435
The end result was that the (potential) future of
the (hypothetical) microprocessor looked
somewhat bleak, but fortunately other forces
were afoot. Although computers were
somewhat scarce in the 1960s, there was a large
and growing market for electronic desktop
calculators. In 1970, the Japanese calculator
company Busicom approached Intel with a
request to design a set of twelve integrated
circuits for use in a new calculator.

436
4004
• The task was presented to Ted Hoff. Hoff realized that
rather than design the special-purpose devices
requested by Busicom, he could create a single
integrated circuit with the attributes of a simple-minded,
stripped-down, general-purpose computer processor.
• The result of Hoff's inspiration was the world's first
microprocessor, the 4004, where the '4's were used to
indicate that the device had a 4-bit data path. The 4004
was part of a four-chip system which also consisted of a
256-byte ROM, a 32-bit RAM, and a 10-bit shift
register. The 4004 itself contained approximately 2,300
transistors and could execute 60,000 operations per
second. The advantage was that by simply changing the
external program, the same device could be used for a
multitude of future projects.

437
The 4004 was the world's first universal
microprocessor. In the late 1960s, many
scientists had discussed the possibility of a
computer on a chip, but nearly everyone felt
that integrated circuit technology was not yet
ready to support such a chip. Intel's Ted Hoff
felt differently; he was the first person to
recognize that the new silicon-gated MOS
technology might make a single-chip CPU
(central processing unit) possible.

438
Hoff and the Intel team developed such an
architecture with just over 2,300 transistors in
an area of only 3 by 4 millimeters. With its 4-
bit CPU, command register, decoder, decoding
control, control monitoring of machine
commands and interim register, the 4004 was
one heck of a little invention. Today's 64-bit
microprocessors are still based on similar
designs, and the microprocessor is still the most
complex mass-produced product ever with
more than 5.5 million transistors performing
hundreds of millions of calculations each
second - numbers that are sure to be outdated
fast.

439
The 4004 was so radically different from
what Busicom had requested that they didn't
immediately recognize its implications (much
as if they'd ordered a Chevy Cavalier, which
had suddenly transmogrified itself into an
Aston Martin), so they politely said that they
weren't really interested and could they please
have the twelve-chip set they'd originally
requested (they did eventually agree to use the
fruits of Hoff's labors).

440
8008
In November 1972, Intel introduced the 8008,
which was essentially an 8-bit version of the
4004. The 8008 contained approximately 3,300
transistors and was the first microprocessor to
be supported by a high-level language compiler
called PL/M. The 8008 was followed by the
4040, which extended the 4004's capabilities by
adding logical and compare instructions, and
by supporting subroutine nesting using a small
internal stack.

441
The Intel 8008 was introduced in April 1972,
and didn't make much of a splash, being more
or less an 8-bit 4004. Its primary claim to fame
is that its ISA -- provided by Computer
Terminal Corporation (CTC), who had
commissioned the chip -- was to form the basis
for the 8080, as well as for the later 8086 (and
hence the x86) architecture. Lesser-known
Intels from this time include the nearly
forgotten 4040, which added logical and
compare instructions to the 4004, and the illfated
32-bit Intel 432.

442
However, the 4004, 4040, and 8008 were
all designed for specific applications, and
it was not until April 1974 that Intel
presented the first true general-purpose
microprocessor, the 8080. This 8-bit
device, which contained around 4,500
transistors and could perform 200,000
operations per second, was destined for
fame as the central processor of many of
the early home computers.

443
8080
The 8080 was the successor to the 8008 . While the
8008 had 14 bit PC and addressing, the 8080 had a
16 bit address bus and an 8 bit data bus. Internally
it had seven 8 bit registers (A-E, H, L - pairs BC,
DE and HL could be combined as 16 bit registers), a
16 bit stack pointer to memory which replaced the 8
level internal stack of the 8008, and a 16 bit
program counter. It also had several I/O ports - 256
of them, so I/O devices could be hooked up without
taking away or interfering with the addressing
space, and a signal pin that allowed the stack to
occupy a separate bank of memory.

444
The 8080 was created by the Intel with
Federico Faggin as the lead designer (his last
chip before he left and started Zilog). The 8080
was released in March of 1974. This chip is
date coded to 1976, so it is a very early version
of the chip. The 8080 was used in the Altair
8800, the first widely-known personal
computer. Because of its increased function and
power over the 4004 and 8008, the 8080 was the
first widely accepted microprocessor. “The
8080 really created the microprocessor market.
The 4004 and 8008 suggested it, but the 8080
made it real.” - Federico Faggin.

445
The 8080 had a 16 bit address bus and an 8 bit
data bus. Internally it had seven 8 bit registers
(A-E, H, L - pairs BC, DE and HL could be
combined as 16 bit registers), a 16 bit stack
pointer to memory which replaced the 8 level
internal stack of the 8008, and a 16 bit program
counter. It also had several I/O ports - 256 of
them, so I/O devices could be hooked up
without taking away or interfering with the
addressing space, and a signal pin that allowed
the stack to occupy a separate bank of memory

446
RCA 1802
In 1974, RCA released the 1802 8-bit
processor with a different architecture than
other 8-bit processors. It had a register file of
16 registers of 16 bits each and using the SEP
instruction, you could select any of the registers
to be the program counter. Using the SEP
instruction, you could choose any of the
registers to be the index register. It did not
have standard subroutine CALL immediate
and RET instructions, though they could be
emulated.
• A few commonly used subroutines could be called
quickly by keeping their address in one of the 16
registers. Before a subroutine returned, it jumped to the
location immediately preceding its entry point so that
after the RET instruction returned control to the caller,
the register would be pointing to the right value for next
time. An interesting variation was to have two or more
subroutines in a ring so that they were called in roundrobin
order.
• The RCA 1802 is considered one of the first RISC chips
although others (notably Seymore Cray -- see the
sidebar, The evolution of RISC -- had used concepts
already).
• Sadly, the RCA chip was a spectacular market failure
due to its slow clock cycle speed. But it could be
fabricated to be radiation resistant, so it was used on the
Voyager 1, Viking, and Galileo space probes (where
rapidly executed commands aren't a necessity).

448
IBM 801
• In 1975, IBM produced some of the earliest efforts to
build a microprocessor based on RISC design
principles (although it wasn't called RISC yet -- see the
sidebar, The evolution of RISC). Initially a research
effort led by John Cocke (the father of RISC), many
say that the IBM 801 was named after the address of
the building where the chip was designed -- but we
suspect that the IBM systems already numbered 601
and 701 had at least something to do with it also.
• The 801 chip family never saw mainstream use, and
was primarily used in other IBM hardware. Even
though the 801 never went far, it did inspire further
work which would converge, fifteen years later, to
produce the Power Architecture family.

449
Moto 6800
• In 1975, Motorola introduced the 6800, a
chip with 78 instructions and probably
the first microprocessor with an index
register.
• Many Motorola stand-alone processors
and microcontrollers trace their lineage
to the 6800, including the popular and
powerful 6809 of 1979

450
Significant Things
• One is the use of the index register which is a
processor register (a small amount of fast computer
memory that's used to speed the execution of
programs by providing quick access to commonly
used values). The index register can modify operand
addresses during the run of a program, typically
while doing vector/array operations.
• Before the invention of index registers and without
indirect addressing, array operations had to be
performed either by linearly repeating program code
for each array element or by using self-modifying
code techniques. Both of these methods harbor
significant disadvantages when it comes to program
flexibility and maintenance and more importantly,
they are wasteful when it comes to using up scarce
computer memory.

451
MOS 6502 • Soon after Motorola released the 6800, the company's
design team quit en masse and formed their own
company, MOS Technology. They quickly developed
the MOS 6501, a completely new design that was
nevertheless pin-compatible with the 6800. Motorola
sued, and MOS agreed to halt production. The
company then released the MOS 6502, which differed
from the 6501 only in the pin-out arrangement.
• Many of the original MOS 6502 still have loving homes
today, in the hands of collectors (or even the original
owners) of machines like the Atari 2600 video game
console, Apple II family of computers, the first
Nintendo Entertainment System, the Commodore 64 --
all of which used the 6502. MOS 6502 processors are
still being manufactured today for use in embedded
systems.

452
The MOS 6502 was released in September 1975,
and it sold for US$25 per unit. At the time, the
Intel 8080 and the Motorola 6800 were selling
for US$179. Many people thought this must be
some sort of scam. Eventually, Intel and
Motorola dropped their prices to US$79. This
had the effect of legitimizing the MOS 6502,
and they began selling by the hundreds. The
6502 was a staple in the Apple® II and various
Commodore and Atari computers.

453
AMD Clones the 8080
• Advanced Micro Devices (AMD) was founded in 1969
by Jerry Sanders. Like so many of the people who
were influential in the early days of the
microprocessor (including the founders of Intel),
Sanders came from Fairchild Semiconductor. AMD's
business was not the creation of new products; it
concentrated on making higher quality versions of
existing products under license. In 1975, it began
selling reverse-engineered clones of the Intel 8080
processor.
• In the 1980s, first licensing agreements -- and then
legal disputes -- with Intel, eventually led to court
validation of clean-room reverse engineering and
opened the 1990s floodgates to many clone corps.

454
Fairchild F8
• The 8-bit Fairchild F8 (also known as the 3850)
microcontroller was Fairchild's first processor. It had
no stack pointer, no program counter, no address bus.
It did have 64 registers (the first 8 of which could be
accessed directly) and 64 bytes of "scratchpad" RAM.
The first F8s were multichip designs (usually 2-chip,
with the second being ROM). The F8 was released in a
single-chip implementation (the Mostek 3870) in 1977.
• The F8 was used in the company's Channel F
Fairchild Video Entertainment System in 1976. By the
end of the decade, Fairchild played mostly in niche
markets, including the "hardened" IC market for
military and space applications, and in Cray
supercomputers. Fairchild was acquired by National
Semiconductor in the 1980s, and spun off again as an
independent company in 1997.

455
16 Bits, Two Contenders
• The first multi-chip 16-bit microprocessor was
introduced by either Digital Equipment
Corporation in its LSI-11 OEM board set and
its packaged PDP 11/03 minicomputer, or by
Fairchild Semiconductor with its MicroFlame
9440, both released in 1975.
• The first single-chip 16-bit microprocessor was
the 1976 TI TMS 9900, which was also
compatible with the TI 990 line of
minicomputers and was used in the TM 990
line of OEM microcomputer boards.

456
• The DEC chipset later gave way to the 32-bit DEC
VAX product line, which was replaced by the Alpha
family, which was discontinued in 2004.
• The aptly named Fairchild MicroFlame ran hot and
was never chosen by a major computer manufacturer,
so it faded out of existence.
• The TI TMS 9900 had a strong beginning, but was
packaged in a large (for the time) ceramic 64-pin
package which pushed the cost out of range compared
with the much cheaper 8-bit Intel 8080 and 8085. In
March 1982, TI decided to start ramping down TMS
9900 production, and go into the DSP business instead.
TI is still in the chip business today, and in 2004 it
came out with a nifty TV tuner chip for cell phones.

457
Zilog Z-80
Probably the most popular
microprocessor of all time, the Zilog Z-80
was designed by Frederico Faggin after
he left Intel, and it was released in July
1976. Faggin had designed or led the
design teams for all of Intel's early
processors: the 4004, the 8008, and
particularly, the revolutionary 8080.
• This 8-bit microprocessor was binary compatible with
the 8080 and surprisingly, is still in widespread use
today in many embedded applications. Faggin intended
it to be an improved version of the 8080 and according
to popular opinion, it was. It could execute all of the
8080 operating codes as well as 80 more instructions
(including 1-, 4-, 8-, and 16-bit operations, block I/O,
block move, and so on). Because it contained two sets of
switchable data registers, it supported fast operating
system or interrupt context switches.
• The thing that really made it popular though, was its
memory interface. Since the CPU generated its own
RAM refresh signals, it provided lower system costs
and made it easier to design a system around. When
coupled with its 8080 compatibility and its support for
the first standardized microprocessor operating system
CP/M, the cost and enhanced capabilities made this the
choice chip for many designers (including TI; it was the
brains of the TRS-80 Model 1).

459
• The Z-80 featured many undocumented instructions
that were in some cases a by-product of early designs
(which did not trap invalid op codes, but tried to
interpret them as best they could); in other cases the
chip area near the edge was used for added instructions,
but fabrication methods of the day made the failure
rate high. Instructions that often failed were just not
documented, so the chip yield could be increased. Later
fabrication made these more reliable.
• In 1979, Zilog announced the 16-bit Z8000. Sporting
another great design with a stack pointer and both a
user and a supervisor mode, this chip never really took
off. However, Zilog is not only still making
microcontrollers, it is still making Z-80
microcontrollers.

460
Intel 8085 and 8086
In 1976, Intel updated the 8080 design with the
8085 by adding two instructions to
enable/disable three added interrupt pins (and
the serial I/O pins). They also simplified
hardware so that it used only +5V power, and
added clock-generator and bus-controller
circuits on the chip. It was binary compatible
with the 8080, but required less supporting
hardware, allowing simpler and less expensive
microcomputer systems to be built. These were
the first Intel chips to be produced without
input from Faggin.

461
• The 8086 chip was released by Intel on June 8, 1978,
after development by a team led by Bill Pohlman. The
8086 was the first processor in the x86 line of
processors which continues right up to the latest
Pentium-III chips. Some of the production of the 8086
chips was subcontracted, the two examples
photographed here were manufactured by Fujitsu
and AMD.
• Although it was the first commercially successful 16
bit processor it was too expensive to implement in
early computers, so a compatible 8 bit version was
developed (the 8088), which was chosen by IBM for
the first IBM PC. It was this choice that resulted in
the chips overwhelming success.
• Intel 8086 microprocessor is a first member of x86
family of processors. Advertised as a "source-code
compatible" with Intel 8080 and Intel 8085 processors,
the 8086 was not object code compatible with them. The
8086 had complete 16-bit architecture - 16-bit internal
registers, 16-bit data bus, and 20-bit address bus (1 MB
of physical memory). Because the processor had 16-bit
index registers and memory pointers, it could effectively
address only 64 KB of memory. To address memory
beyond 64 KB the Intel 8086 used segment registers -
these registers specified where code, stack data and
extra data 64 KB segments are located within 1 MB of
total processor memory.
• To accommodate this awkward memory addressing
many 8086 compilers included 6 different memory
models: tiny, small, compact, medium, large and huge.
64 KB direct addressing limitation went away with the
introduction of the 32-bit protected mode in Intel 80386
processor.

463
• The 8086 itself wasn't used by IBM until the
PS/2 model 25 and model 30 in 1987, although
IBM clones had used it long before this.
• The available clock frequencies are 4.77, 8 and
10 MHz. It has an instruction set of about 300
operations. At introduction the fastest
processor was the 8 MHz version which
achieved 0.8 MIPs and contained 29,000
transistors.

464
8088
Intel 8088 microprocessor is almost identical to
the Intel 8086 processor with the exception of
the external data bus. External data bus width
of the 8088 was reduced to 8 bits, and
instruction queue size and prefetching
algorithms were changed. Intel 8088 used two
consecutive bus cycles to write or read 16 bit
data instead of one cycle for the 8086. This
made the processor to run slower, but on the
plus side the hardware changes in the 8088
CPU made it compatible with 8080/8085
peripherals.

465
Architecture of the 8088 stayed the same as the
8086: 16-bit registers, 16-bit internal data bus
and 20-bit address bus, which allowed the
processor address up to 1 MB of memory. The
8088 had the same segmented memory
addressing as the 8086: the processor could
address 64 KB of memory directly, and to
address more than 64 KB of memory one of
special segment registers had to be updated.

466
Moto 68000
• In 1979, Motorola introduced the 68000. With internal
32-bit registers and a 32-bit address space, its bus was
still 16 bits due to hardware prices. Originally designed
for embedded applications, its DEC PDP-11 and VAXinspired
design meant that it eventually found its way
into the Apple Macintosh, Amiga, Atari, and even the
original Sun Microsystems® and Silicon Graphics
computers.
• As the 68000 was reaching the end of its life, Motorola
entered into the Apple-IBM-Motorola "AIM" alliance
which would eventually produce the first PowerPC®
chips. Motorola ceased production of the 68000 in 2000.

467
6.4 Dawning of RISC Age: The 1980s
•Advances in process ushered in the "more is more" era
of VLSI, leading to true 32-bit architectures. At the same
time, the "less is more" RISC philosophy allowed for
greater performance. When combined, VLSI and RISC
produced chips with awesome capabilities, giving rise to
the UNIX workstation market.
•The decade opened with intriguing contemporaneous
independent projects at Berkeley and Stanford -- RISC
and MIPS. Even with the new RISC families, an
industry shakeout commonly referred to as "the
microprocessor wars," would mean that we left the
1980s with fewer major micro manufacturers than we
had coming in.
•By the end of the decade, prices had dropped
substantially, so that record numbers of households and
schools had access to more computers than ever before.

468
Berkeley RISC
• In 1980, the University of California at
Berkeley started something it called the RISC
Project (in fact, the professors leading the
project, David Patterson and Carlo H. Sequin,
are credited with coining the term "RISC").
• The project emphasized pipelining and the use
of register windows: by 1982, they had
delivered their first processor, called the RISCI.
With only 44KB transistors (compared with
about 100KB in most contemporary processors)
and only 32 instructions, it outperformed any
other single chip design in existence.

469
By 1983, the RISC Project at Berkeley
had produced the RISC-II which
contained 39 instructions and ran more
than 3 times as fast as the RISC-I. Sun
Microsystem's SPARC (Scalable
Processor ARChitecture) chip design is
heavily influenced by the minimalist
RISC Project designs of the RISC-I and -
II.

470
RISC was quickly adopted in the industry, and
today remains the most popular architecture
for processors. During the 1980s, several
additional RISC families were launched. Aside
from those already mentioned above were:
• CRISP (C Reduced Instruction Set Processor)
from AT&T Bell Labs.
• The Motorola 88000 family.
• Digital Equipment Corporation Alpha's (the
world's first single-chip 64-bit microprocessor).
• HP Precision Architecture (HP PA-RISC).

471
MIPS
Meanwhile, in 1981, and just across the San
Francisco Bay from Berkeley, John Hennessy
and a team at Stanford University started
building what would become the first MIPS
processor. They wanted to use deep instruction
pipelines -- a difficult-to-implement practice --
to increase performance. The MIPS design
settled on a relatively simple demand to
eliminate interlocking -- all instructions must
take only one clock cycle. This was a potentially
useful alteration in the RISC philosophy.

472
• MIPS was used in Silicon Graphics
workstations for years. Although SGI's newest
offerings now use Intel processors, MIPS is
very popular in embedded applications.
• Professor Hennessy left Stanford in 1984 to
form MIPS Computers. The company's
commercial 32-bit designs implemented the
interlocks in hardware. MIPS was purchased
by Silicon Graphics, Inc. in 1992, and was spun
off as MIPS Technologies, Inc. in 1998. John
Hennessy is currently Stanford University's
tenth President.

473
POWER
• Also contemporaneously and independently,
IBM continued to work on RISC as well. 1974's
801 project turned into Project America and
Project Cheetah. Project Cheetah would
become the first workstation to use a RISC
chip, in 1986: the PC/RT, which used the 801-
inspired ROMP chip.
• IBM's Cheetah project, which developed into
the PC-RT's ROMP, was a bit of a flop, but
Project America was in prototype by 1985 and
would, in 1990, become RISC System/6000. Its
processor would be renamed the POWER1.

474
Intel Microprocessor Family
• Intel 80186 microprocessor, sometimes called
i186, is an enhanced version of Intel 8086 16-bit
processor. Being completely object code
compatible with the 8086, the 80186 integrated
many system components into one chip, added 7
new instructions, and added new operand types
to three existing 8086 instructions. With the
exception of integrated components, the Intel
80186 microprocessor is not very different from
the 8086, and, because of this, the 80186 may be
considered as an embedded version of 8086.

475
• The 80186 didn't even have its own version of coprocessor
and worked with Intel 8087. Although
the Intel 80186 was not widely used in the
computers as the 8086 and 80286 did, it was
successful in embedded processor market. In fact,
the processor was so successful, that many
different versions of the processor were
introduced over last 20 years - 80C186, 80186EA,
80186EB, etc. At this time (November 2004) some
of these versions are still in production.

476
Intel 80286 is a next generation of 8086 16-bit
processor. The 80286 microprocessor included new
instructions that were introduced by 80188/80186
processors, and added new features:
• New 16-bit protected mode allowed the processor to
access 16 MB of memory. To setup the protected
mode new instructions and registers were added to
the 80286.
• Execution time of many instructions was reduced.
• The 80286 microprocessor was produced at speeds
ranging from 4 MHz to 25 MHz.

477
32-bitness
The early 1980s also saw the first 32-bit
chips arrive in droves.

478
BELLMAC-32A
AT&T's Computer Systems division opened its doors
in 1980, and by 1981 it had introduced the world's
first single-chip 32-bit microprocessor, the AT&T Bell
Labs' BELLMAC-32A, (it was renamed the WE 32000
after the break-up in 1984). There were two
subsequent generations, the WE 32100 and WE 32200,
which were used in:
• the 3B5 and 3B15 minicomputers
• the 3B2, the world's first desktop supermicrocomputer
• the "Companion", the world's first 32-bit laptop
computer
• "Alexander", the world's first book-sized
supermicrocomputer
• All ran the original Bell Labs UNIX.

479
Motorola 68010
Motorola had already introduced the MC
68000, which had a 32-bit architecture
internally, but a 16-bit pinout externally.
It introduced its pure 32-bit
microprocessors, the MC 68010, 68012,
and 68020 by 1985 or thereabouts, and
began to work on a 32-bit family of RISC
processors, named 88000.

480
NS 32032
In 1983, National Semiconductor
introduced a 16-bit pinout, 32-bit internal
microprocessor called the NS 16032, the
full 32-bit NS 32032, and a line of 32-bit
industrial OEM microcomputers.
Sequent also introduced the first
symmetric multiprocessor (SMP) serverclass
computer using the NS 32032.

481
• Intel entered the 32-bit world in 1981, same as
the AT&T BELLMAC chips, with the ill-fated
432. It was a three-chip design rather than a
single-chip implementation, and it didn't go
anywhere. In 1986, its 32-bit i386 became its
first single-chip 32-bit offering, closely followed
by the 486 in 1989.
• AT&T closed its Computer Systems division in
December, 1995. The company shifted to MIPS
and Intel chips.

482
Intel Processor Family
The third generation of x86 family, the
Intel 80386 (i386) was a complete 32-bit
processor with ability to address 4 GB
of physical memory. The processor
included new protected mode, that
allowed the processor to fully utilize
new 32-bit architecture and new
features. Another new mode - virtual
mode - could be used to run old 8086
applications without switching the
processor back from protected mode to
real mode.

483
• 80386DX has 32-bit external data and address
busses.
• Low cost 80386SX had 16 bit external data bus
and 24-bit external address bus. This processor
supported only 16 MB of physical memory.
• Low-power 80386SL with power management
features, with 16-bit external data bus and 24-
bit external address bus.
• Embedded 80376 and 80386EX processors.
• The Intel 80386 was produced at speeds up to
33 MHz, AMD produced even faster 40 MHz
version.

484
The successor to the 80386 processor, Intel 80486 (i486)
added new important features:
• Floating Point Unit was integrated with the processor
• Internal clock doubling and tripling allowed the
processor to run much faster in existing motherboards.
• Power management features and SMM (System
Management Mode) became a standard feature of the
processor.
• Instruction set optimization resulted in even greater
performance of the processor. Different versions of the
80486 were produced, two most common versions are
80486DX with integrated FPU, and 80486SX without
FPU. The Intel 80486 was produced at speeds up to
100 MHz. AMD produced even faster 120 and 133
MHz versions of the 80486.

485
ARM is born
• In 1983, Acorn Computers Ltd. was looking for a
processor. Some say that Acorn was refused access to
Intel's upcoming 80286 chip, others say that Acorn
rejected both the Intel 286 and the Motorola MC 68000
as being not powerful enough. In any case, the
company decided to develop its own processor called
the Acorn RISC Machine, or ARM.
• However, the company's ARM architecture today
accounts for approximately 75% of all 32-bit
embedded processors. The most successful
implementation has been the ARM7TDMI with
hundreds of millions sold in cellular phones. The
Digital/ARM combo Strong ARM is the basis for the
Intel XScale processor.

486
6.5 A New Hope: The 1990s
• By 1991, the Cold War was officially at an end. Those
high-end UNIX workstation vendors who were left
standing after the "microprocessor wars" scrambled
to find new, non-military markets for their wares.
Luckily, the commercialization and broad adoption of
the Internet in the 1990s neatly stepped in to fill the
gap.
• For at the beginning of that decade, you couldn't run
an Internet server or even properly connect to the
Internet on anything but UNIX. A side effect of this
was that a large number of new people were
introduced to the open-standards Free Software that
ran the Internet.

487
• The popularization of the Internet led to higher
desktop sales as well, fueling growth in that sector.
Throughout the 1990s, desktop chipmakers
participated in a mad speed race to keep up with
"Moore's Law" -- often neglecting other areas of
their chips' architecture to pursue elusive clock rate
milestones.
• 32-bitness, so coveted in the 1980s, gave way to 64-
bitness. The first high-end UNIX processors would
blazon the 64-bit trail at the very start of the 1990s,
and by the time of this writing, most desktop systems
had joined them. The POWER™ and PowerPC
family, introduced in 1990, had a 64-bit ISA from
the beginning.

488
Power Architecture
• IBM introduced the POWER architecture -- a
multichip RISC design -- in early 1990. By the
next year, the first single-chip PowerPC
derivatives (the product of the Apple-IBMMotorola
AIM alliance) were available as a
high-volume alternative to the predominating
CISC desktop structure.
• Power Architecture technology is popular in all
markets, from the high-end UNIX eServer™ to
embedded systems. When used on the desktop,
it is often known as the Apple G5. The
cooperative climate of the original AIM alliance
has been expanded into an organization by
name of Power.org.

489
DEC Alpha
In 1992, DEC introduced the Alpha 21064 at a
speed of 200MHz. The superscalar,
superpipelined 64-bit processor design was
pure RISC, but it outperformed the other chips
and was referred to by DEC as the world's
fastest processor. (When the Pentium was
launched the next spring, it only ran at 66MHz.)
The Alpha too was intended to be used in both
UNIX server/workstations as well as desktop
variants.

490
The primary contribution of the Alpha design
to microprocessor history was not in its
architecture -- that was pure RISC. The
Alpha's performance was due to excellent
implementation. The microchip design process
is dominated by automated logic synthesis
flows. To deal with the extremely complex VAX
architecture, Digital designers applied human,
individually crafted attention to circuit design.
When this was applied to a simple, clean
architecture like the RISC-based Alpha, the
combination gleaned the highest possible
performance.

491
Sadly, the very thing that led Alpha
down the primrose path -- hand-tuned
circuits -- would prove to be its undoing.
As DEC was going out of business, its
chip division, Digital Semiconductor, was
sold to Intel as part of a legal settlement.
Intel used the StrongARM (a joint
project of DEC and ARM) to replace its
i860 and i960 line of RISC processors.

492
The Clone Wars Begin
In March 1991, Advanced Micro Devices
(AMD) introduced its clone of Intel's i386DX.
It ran at clock speeds of up to 40MHz. This set
a precedent for AMD -- its goal was not just
cheaper chips that would run code intended for
Intel-based systems, but chips that would also
outperform the competition. AMD chips are
RISC designs internally; they convert the Intel
instructions to appropriate internal operations
before execution.

493
• Also in 1991, litigation between AMD and
Intel was finally settled in favor of AMD,
leading to a flood of clonemakers --
among them, Cyrix, NexGen, and others -
- few of which would survive into the next
decade.
• In the desktop space, Moore's Law
turned into a Sisyphean treadmill as
makers chased elusive clock speed
milestones.

494
• Well, of course, AMD is still standing. In
fact, its latest designs are being cloned by
Intel!
• Cyrix was acquired by National
Semiconductor in 1997, and sold to VIA
in 1999. The acquisition turned VIA into
a processor player, where it had mainly
offered core logic chipsets before. The
company today specializes in highperformance,
low-power chips for the
mobile market.

495
Intel Pentium I
Year:1993
Fifth generation of x86 processors:
superscalar architecture, MMX. The
processor has 3,100,000 transistors, and
can address 4 GB of physical memory
and 64 TB of virtual memory.

496
Intel Pentium II Intel Pentium II line of processors is based on sixth
generation x86 processor core. The Intel Pentium II
line consists of 6 different families:
• Pentium Pro - high performance version. The
Pentium Pro family was replaced by the Pentium II
Xeon family.
• Pentium II - desktop family.
• Mobile Pentium II - mobile version of the Pentium II
processor.
• Pentium II Xeon - high performance version.
• Desktop Celeron - low-cost version.
• Mobile Celeron - mobile version of Intel Celeron
processor.

497
Intel Pentium III
Year:1999
• Enhanced version of Pentium II processor
• The Pentium III processor is for high
performance applied computing. It supports
highend communications, transaction terminal,
and industrial automation applications. While
incorporating new features and improvements,
the Pentium III processor remains software
compatible with previous members of the Intel
microprocessor family.

498
The Pentium III processor is validated with multiple
chipsets for maximum flexibility and scalability.
Combined with the Intel 840 chipset, the Pentium III
processor provides high performance and bandwidth
including dual processing and a second PCI bus. The 815,
815E, 810 and 440BX chipsets provide a scalable
platform supporting a wide selection of Celeron and
Pentium III processors ranging from 66 to 133 MHz
processor side bus speeds. The 440BX AGPset supports
ECC for the highest data integrity and ISA for legacy
I/O. The Intel 815, 815E and 810 chipsets utilize Intel
Graphics Technology, an integrated graphics platform
which provides more stability, higher quality graphics
and a reduced OEM bill of materials cost.

499
Intel Pentium 4
Year:2000
• Next generation of Pentium processors.
• The Intel Pentium 4 Processor is designed to
deliver performance across usages—such as
image processing, video content creation,
games and multimedia—where end-users can
truly appreciate the performance. With a PC
based on the Intel Pentium 4 Processor with
HT Technology†, you get advanced
performance and multitasking capabilities for
today's digital home and digital office
applications.

500
•Improved Power Management with Enhanced Intel
Speed Step Technology. Intel Pentium 4 Processors that
are enabled with Enhanced Intel Speed Step Technology
allow the operating system to adjust the processor clock
down when running applications that require less power.
Increased power efficiency brings savings.
•Scalability and performance with Intel EM64T
Intel Extended Memory 64 Technology (Intel EM64T)
can improve performance by allowing the system to
address more than 4 GB of both virtual and physical
memory. Intel EM64T also provides support for 64 bit
computing to help handle the applications of tomorrow.
•Execute Disable Bit functionality protects your
investment. Execute Disable Bit can prevent certain
classes of malicious "buffer overflow" attacks when
combined with a supporting operating system.

501
6.6 Where are We Now? The 2000s
The 2000s have come along and it's too early
yet to say what will have happened by decade's
end. As Federico Faggin said, the exponential
progression of Moore's law cannot continue
forever. As the day nears when process will be
measured in Angstroms instead of nanometers,
researchers are furiously experimenting with
layout, materials, concepts, and process. After
all, today's microprocessors are based on the
same architecture and processes that were first
invented 30 years ago -- something has
definitely got to give.

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