IBM PC compatible
IBM PC compatible computers are computers similar to the original IBM
PC, XT, and AT, able to use the same software and expansion cards .
Such computers used to be referred to as PC clones, or IBM clones.
They duplicate almost exactly all the significant features of the PC
architecture, facilitated by IBM's choice of commodity hardware
components and various manufacturers' ability to reverse engineer the
BIOS firmware using a "clean room design" technique. Columbia Data
Products built the first clone of the IBM personal computer by a clean
room implementation of its BIOS.
Early IBM PC compatibles used the same computer bus as the original PC
and AT models. The IBM AT compatible bus was later named the Industry
Standard Architecture (ISA) bus by manufacturers of compatible
computers. The term "IBM PC compatible" is now a historical
description only, since IBM has ended its personal computer sales.
Descendants of the IBM PC compatibles comprise the majority of
personal computers on the market presently with the dominant operating
Microsoft Windows, although interoperability with the bus
structure and peripherals of the original PC architecture may be
limited or non-existent. Some models of computers were made that ran
MS-DOS as did the PC, but which had enough differences in the hardware
that IBM compatible software could not be used, for example, because
of slight differences in the memory map, or in the serial ports or
video hardware. Only the
Macintosh kept significant market share
without compatibility with the IBM PC.
2 Compatibility issues
2.2 "Operationally Compatible"
3 The decreasing influence of IBM
5 "IBM PC compatible" becomes "Wintel"
6 Design limitations and more compatibility issues
7 Challenges to
IBM PC compatible
IBM PC compatible today
9 See also
The original IBM PC (Model 5150) motivated the production of clones
during the early 1980s.
IBM decided in 1980 to market a low-cost single-user computer as
quickly as possible in response to Apple Computer's
success in the burgeoning microcomputer market. On 12 August 1981, the
first IBM PC went on sale. There were three operating systems (OS)
available for it. The least expensive and most popular was
PC DOS made
by Microsoft. In a crucial concession, IBM's agreement allowed
Microsoft to sell its own version, MS-DOS, for non-IBM computers. The
only component of the original PC architecture exclusive to IBM was
BIOS (Basic Input/Output System).
IBM at first asked developers to avoid writing software that addressed
the computer's hardware directly, and to instead make standard calls
BIOS functions that carried out hardware-dependent operations.
This software would run on any machine using
MS-DOS or PC-DOS.
Software that directly addressed the hardware instead of making
standard calls was faster, however; this was particularly relevant to
games. Software addressing IBM PC hardware in this way would not run
MS-DOS machines with different hardware. The IBM PC was sold in
high enough volumes to justify writing software specifically for it,
and this encouraged other manufacturers to produce machines which
could use the same programs, expansion cards, and peripherals as the
PC. The 808x computer marketplace rapidly excluded all machines which
were not hardware- and software-compatible with the PC. The
640 KB barrier on "conventional" system memory available to
MS-DOS is a legacy of that period; other non-clone machines, while
subject to a limit, could exceed 640 kB.
Rumors of "lookalike", compatible computers, created without IBM's
approval, began almost immediately after the IBM PC's release.
InfoWorld wrote on the first anniversary of the IBM PC that
The dark side of an open system is its imitators. If the specs are
clear enough for you to design peripherals, they are clear enough for
you to design imitations. Apple ... has patents on two important
components of its systems ... IBM, which reportedly has no special
patents on the PC, is even more vulnerable. Numerous PC-compatible
machines—the grapevine says 60 or more—have begun to appear in the
By June 1983
PC Magazine defined "PC 'clone'" as "a computer [that
can] accommodate the user who takes a disk home from an IBM PC, walks
across the room, and plugs it into the 'foreign' machine". Because
of a shortage of IBM PCs that year, many customers purchased clones
Columbia Data Products
Columbia Data Products produced the first computer more
or less compatible with the IBM PC standard during June 1982, soon
followed by Eagle Computer.
Compaq announced its first IBM PC
compatible in November 1982, the
Compaq Portable. The
Compaq was the
first sewing machine-sized portable computer that was essentially 100%
PC-compatible. The company could not copy the
BIOS directly as a
result of the court decision in Apple v. Franklin, but it could
reverse-engineer the IBM
BIOS and then write its own
BIOS using clean
See also: Influence of the IBM PC on the personal computer market
Compaq Portable was the first 100% IBM-compatible PC, and the
first portable one.
MS-DOS version 1.12 for
Compaq Personal Computers
At the same time, many manufacturers such as Tandy/RadioShack, Xerox,
Hewlett-Packard, Digital Equipment Corporation, Sanyo, Texas
Instruments, Tulip, Wang and
Olivetti introduced personal computers
that supported MS DOS, but were not completely software- or
hardware-compatible with the IBM PC.
Tandy described the Tandy 2000, for example, as having a "'next
generation' true 16-bit CPU", and with "More speed. More disk storage.
More expansion" than the IBM PC or "other
MS-DOS computers". While
admitting in 1984 that many
MS-DOS programs did not support the
computer, the company stated that "the most popular, sophisticated
software on the market" was available, either immediately or "over the
next six months".
Like IBM, Microsoft's intention was that application writers would
write to the application programming interfaces in
MS-DOS or the
firmware BIOS, and that this would form what would now be termed a
hardware abstraction layer. Each computer would have its own Original
Equipment Manufacturer (OEM) version of MS-DOS, customized to its
hardware. Any software written for
MS-DOS would operate on any MS-DOS
computer, despite variations in hardware design.
This expectation seemed reasonable in the computer marketplace of the
time. Until then
Microsoft was based primarily on computer languages
such as BASIC. The established small system operating software was
Digital Research which was in use both at the hobbyist level
and by the more professional of those using microcomputers. To achieve
such widespread use, and thus make the product viable economically,
the OS had to operate across a range of machines from different
vendors that had widely varying hardware. Those customers who needed
other applications than the starter programs could reasonably expect
publishers to offer their products for a variety of computers, on
suitable media for each.
Microsoft's competing OS was intended initially to operate on a
similar varied spectrum of hardware, although all based on the 8086
MS-DOS was for several years sold only as an OEM
product. There was no Microsoft-branded MS-DOS:
MS-DOS could not be
purchased directly from Microsoft, and each OEM release was packaged
with the trade dress of the given PC vendor. Malfunctions were to be
reported to the OEM, not to Microsoft. However, as machines that were
compatible with IBM hardware—thus supporting direct calls to the
hardware—became widespread, it soon became clear that the OEM
MS-DOS were virtually identical, except perhaps for the
provision of a few utility programs.
MS-DOS provided adequate functionality for character-oriented
applications such as those that could have been implemented on a
text-only terminal. Had the bulk of commercially important software
been of this nature, low-level hardware compatibility might not have
mattered. However, in order to provide maximum performance and
leverage hardware features (or work around hardware bugs), PC
applications quickly developed beyond the simple terminal applications
MS-DOS supported directly. Spreadsheets,
WYSIWYG word processors,
presentation software and remote communication software established
new markets that exploited the PC's strengths, but required
capabilities beyond what
MS-DOS provided. Thus, from very early in the
development of the
MS-DOS software environment, many significant
commercial software products were written directly to the hardware,
for a variety of reasons:
MS-DOS itself did not provide any way to position the text cursor
other than to advance it after displaying each letter (teletype mode).
BIOS video interface routines were adequate for rudimentary
output, they were necessarily less efficient than direct hardware
addressing, as they added extra processing; they did not have "string"
output, but only character-by-character teletype output, and they
inserted delays to prevent CGA hardware "snow" (a display artifact of
CGA cards produced when writing directly to screen memory)——an
especially bad artifact since they were called by IRQs, thus making
multitasking very difficult. A program that wrote directly to video
memory could achieve output rates 5 to 20 times faster than making
Turbo Pascal used this technique from its earliest
Graphics capability was not taken seriously in the original IBM design
brief; graphics were considered only from the perspective of
generating static business graphics such as charts and graphs. MS-DOS
did not have an API for graphics, and the
BIOS only included the
rudimentary graphics functions such as changing screen modes and
plotting single points. To make a
BIOS call for every point drawn or
modified increased overhead considerably, making the
notoriously slow. Because of this, line-drawing, arc-drawing, and
blitting had to be performed by the application to achieve acceptable
speed, which was usually done by bypassing the
BIOS and accessing
video memory directly. Software written to address IBM PC hardware
directly would run on any IBM clone, but would have to be rewritten
especially for each non-PC-compatible
Video games, even early ones, mostly required a true graphics mode.
They also performed any machine-dependent trick the programmers could
think of in order to gain speed. Though initially the major market for
the PC was for business applications, games capability became an
important factor motivating PC purchases as prices decreased. The
availability and quality of games could mean the difference between
the purchase of a PC compatible or a different platform with the
ability to exchange data like the Amiga.
Communications software directly accessed the UART serial port chip,
MS-DOS API and the
BIOS did not provide full support and
was too slow to keep up with hardware which could transfer data at
Even for standard business applications, speed of execution was a
significant competitive advantage.
Integrated software Context MBA
Lotus 1-2-3 to market and included more functions. Context
MBA was written in UCSD p-System, making it very portable but too slow
to be truly usable on a PC. 1-2-3 was written in x86 assembly language
and performed some machine-dependent tricks. It was so much faster
that it quickly surpassed Context MBA's sales.
Disk copy-protection schemes, in common use at the time, worked by
reading nonstandard data patterns on the diskette to verify
originality. These patterns were impossible to detect using standard
BIOS calls, so direct access to the disk controller hardware
was necessary for the protection to work.
Some software was designed to run only on a true IBM PC, and checked
for an actual IBM BIOS.
PC compatibility was an important concern. Even the Commodore Amiga
1000 had a PC compatible add-on module, the Sidecar.
In May 1983, Future Computing defined four levels of
Operationally Compatible. Can run "the top selling" IBM PC software,
use PC expansion boards, and read and write PC disks. Has
"complementary features" like portability or lower price that
distinguish computer from the PC, which is sold in the same store.
Examples: (Best) Columbia Data Products, Compaq; (Better) Corona;
Functionally Compatible. Runs own version of popular PC software.
Cannot use PC expansion boards but can read and write PC disks. Cannot
become Operationally Compatible. Example: TI Professional.
Data Compatible. May not run top PC software. Can read and/or write PC
disks. Can become Functionally Compatible. Examples: NCR Decision
Olivetti M20, Wang PC, Zenith Z-100.
Incompatible. Cannot read PC disks. Can become Data Compatible.
Examples: Altos 586, DEC Rainbow 100, Grid Compass, Victor 9000.
Compaq engineers found that
Simulator would not run because of what subLOGIC's Bruce Artwick
described as "a bug in one of Intel's chips", forcing them to make
their new computer bug compatible with the IBM PC. At first, few
clones other than Compaq's offered truly full compatibility;
Columbia University reported in January 1984, for example, that Kermit
ran without modification on
Columbia Data Products
Columbia Data Products clones,
but not on those from Eagle or Seequa. Other
MS-DOS computers also
required custom code.
Many companies were reluctant to have their products' PC compatibility
PC Magazine requested samples from computer manufacturers
that claimed to produce compatibles for an April 1984 review, 14 of 31
Corona Data Systems
Corona Data Systems specified that "Our systems run
all software that conforms to IBM PC programming standards. And the
most popular software does." When a
BYTE journalist asked to test
Peachtext at the Spring 1983 COMDEX, Corona representatives "hemmed
and hawed a bit, but they finally led me ... off in the corner where
no one would see it should it fail". The magazine reported that "Their
hesitancy was unnecessary. The disk booted up without a problem".
Zenith Data Systems
Zenith Data Systems was bolder, bragging that its Z-150 ran all
applications people brought to test with at the 1984 West Coast
Creative Computing in 1985 stated, "we reiterate our standard line
regarding the IBM PC compatibles: try the package you want to use
before you buy the computer." Companies modified their computers'
BIOS to work with newly discovered incompatible applications, and
reviewers and users developed stress tests to measure compatibility;
by 1984 the ability to operate
Lotus 1-2-3 and Flight Simulator became
the standard, with compatibles specifically
designed to run them.
IBM believed that some companies such as Eagle, Corona, and Handwell
infringed on its copyright, and after Apple Computer, Inc. v. Franklin
Computer Corp. successfully forced the clone makers to stop using the
BIOS. The Phoenix
BIOS in 1984, however, and similar products such as
AMI BIOS, permitted computer makers to legally build essentially
100%-compatible clones without having to reverse-engineer the PC BIOS
themselves. A September 1985
InfoWorld chart listed seven
compatibles with 256 KB RAM, two disk drives, and monochrome
monitors for $1,495 to $2,320, while the equivalent IBM PC cost
$2,820. By 1986
Compute! stated that "clones are generally
reliable and about 99 percent compatible".
The decreasing influence of IBM
In February 1984 Byte wrote that "IBM's burgeoning influence in the PC
community is stifling innovation because so many other companies are
mimicking Big Blue", but as the market grew IBM's influence
diminished. In November 1985
PC Magazine stated "Now that it has
created the [PC] market, the market doesn't necessarily need IBM for
the machines. It may depend on IBM to set standards and to develop
higher-performance machines, but IBM had better conform to existing
standards so as to not hurt users". In January 1987 Bruce Webster
wrote in Byte of rumors that IBM would introduce proprietary personal
computers with a proprietary operating system: "Who cares? If IBM does
it, they will most likely just isolate themselves from the largest
marketplace, in which they really can't compete anymore anyway". The
magazine predicted that in 1987 the market "will complete its
transition from an IBM standard to an Intel/MS-DOS/expansion bus
standard ... Folks aren't so much concerned about IBM compatibility as
they are about
Lotus 1-2-3 compatibility". By 1992
that because of clones, "IBM lost control of its own market and became
a minor player with its own technology".
After IBM announced the OS/2-oriented
PS/2 line in early 1987, sales
of existing DOS-compatible PC compatibles rose, in part because the
proprietary operating system was not available. In 1988 Gartner
Group estimated that the public purchased 1.5 clones for every IBM
PC. By 1989
Compaq was so influential that industry executives
spoke of "
Compaq compatible", with observers stating that customers
saw the company as IBM's equal.
After 1987, IBM PC compatibles dominated both the home and business
markets of commodity computers, with other notable alternative
architectures being used in niche markets, like the Macintosh
computers offered by
Apple Inc. and used mainly for desktop publishing
at the time, the aging 8-bit
Commodore 64 which was selling for $150
by this time and became the world's best-selling computer, the 32-bit
Amiga line used for television and video production and the
Atari ST used by the music industry. However, IBM itself lost
the main role in the market for IBM PC compatibles by 1990. A few
events in retrospect are important:
IBM designed the PC with an open architecture which permitted clone
makers to use freely available non-proprietary components.
Microsoft included a clause in its contract with IBM which permitted
the sale of the finished PC operating system (PC DOS) to other
computer manufacturers. These IBM competitors licensed it, as MS-DOS,
in order to offer PC compatibility for less cost.
The 1982 introduction of the
Compaq Portable, the first 100% IBM PC
compatible computer, providing portability unavailable from IBM at the
An Independent Business Unit (IBU) within IBM developed the IBM PC and
XT. IBUs did not share in corporate R&D expense. After the IBU
became the Entry Systems Division it lost this benefit, greatly
The availability by 1986 of sub-$1000 "Turbo XT"
PC XT compatibles,
including early offerings from Dell Computer, reducing demand for
IBM's models. It was possible to buy two of these "generic"
systems for less than the cost of one IBM-branded PC AT, and many
companies did just that.
Compaq beating IBM to market during 1986 with
Compaq Deskpro 386, the
first 80386-based PC.
IBM's 1987 introduction of the incompatible and proprietary
MicroChannel Architecture (MCA) computer bus, for its Personal
System/2 (PS/2) line.
The 1988 introduction by the "Gang of Nine" companies of a rival bus,
Extended Industry Standard Architecture, intended to compete with,
rather than copy, MCA.
The duelling expanded memory (EMS) and extended memory (XMS) standards
of the late 1980s, both developed without input from IBM.
Despite popularity of its
ThinkPad set of laptop PC's, IBM finally
relinquished its role as a consumer PC manufacturer during April 2005,
when it sold its laptop and desktop PC divisions to
Lenovo for US$1.75
As of October 2007,
Hewlett-Packard and Dell have the largest shares
of the PC market in North America. They are also successful overseas,
with Acer, Lenovo, and
Toshiba also notable. Worldwide, a huge number
of PCs are "white box" systems assembled by myriad local systems
builders. Despite advances of computer technology, all current IBM PC
compatibles remain very much compatible with the original IBM PC
computers, although most of the components implement the compatibility
in special backward compatibility modes used only during a system
boot. It is often more practical to run old software on a modern
system using an emulator rather than relying on these features.
Lenovo acquired IBM's x86-based server business for US$2.1
One of the strengths of the PC compatible design is its modular
hardware design. End-users could readily upgrade peripherals and, to
some degree, processor and memory without modifying the computer's
motherboard or replacing the whole computer, as was the case with many
of the microcomputers of the time. However, as processor speed and
memory width increased, the limits of the original XT/AT bus design
were soon reached, particularly when driving graphics video cards. IBM
did introduce an upgraded bus in the IBM
PS/2 computer that overcame
many of the technical limits of the XT/AT bus, but this was rarely
used as the basis for IBM compatible computers since it required
licence payments to IBM both for the
PS/2 bus and any prior AT-bus
designs produced by the company seeking a license. This was unpopular
with hardware manufacturers and several competing bus standards were
developed by consortiums, with more agreeable license terms. Various
attempts to standardize the interfaces were made, but in practice,
many of these attempts were either flawed or ignored. Even so, there
were many expansion options, and despite the confusion of its users,
the PC compatible design advanced much faster than other competing
designs of the time, even if only because of its market dominance.
"IBM PC compatible" becomes "Wintel"
During the 1990s, IBM's influence on PC architecture started to
decline. An IBM-brand PC became the exception rather than the rule.
Instead of placing importance on compatibility with the IBM PC,
vendors began to emphasize compatibility with Windows. In 1993, a
Windows NT was released that could operate on processors
other than the x86 set. While it required that applications be
recompiled, which most developers did not do, its hardware
independence was used for
Silicon Graphics (SGI) x86
workstations–thanks to NT's
Hardware abstraction layer (HAL), they
could operate NT (and its vast application library)[clarification
No mass-market personal computer hardware vendor dared to be
incompatible with the latest version of Windows, and Microsoft's
annual WinHEC conferences provided a setting in which
lobby for—and in some cases dictate—the pace and direction of the
hardware of the PC industry.
Microsoft and Intel had become so
important to the ongoing development of PC hardware that industry
writers began using the word
Wintel to refer to the combined
This terminology itself is becoming a misnomer, as Intel has lost
absolute control over the direction of x86 hardware development with
AMD's AMD64. Also, non-Windows operating systems like macOS and Linux
have established a presence on the x86 architecture.
Design limitations and more compatibility issues
Although the IBM PC was designed for expandability, the designers
could not anticipate the hardware developments of the 1980s, nor the
size of the industry they would engender. To make things worse, IBM's
choice of the
Intel 8088 for the CPU introduced several limitations
for developing software for the PC compatible platform. For example,
the 8088 processor only had a 20-bit memory addressing space. To
expand PCs beyond one megabyte, Lotus, Intel, and
created expanded memory (EMS), a bank-switching scheme to allow more
memory provided by add-in hardware, and accessed by a set of four
Kilobyte "windows" inside the 20-bit addressing. Later, Intel CPUs
had larger address spaces and could directly address 16- megabytes
(MiBs) (80286) or more, causing
Microsoft to develop extended memory
(XMS) which did not require additional hardware.
"Expanded" and "extended" memory have incompatible interfaces, so
anyone writing software that used more than one megabyte had to
provide for both systems for the greatest compatibility until MS-DOS
began including EMM386, which simulated EMS memory using XMS memory. A
protected mode OS can also be written for the 80286, but DOS
application compatibility was more difficult than expected, not only
because most DOS applications accessed the hardware directly,
BIOS routines intended to ensure compatibility, but also
BIOS requests were made by the first 32 interrupt vectors,
which were marked as "reserved" for protected mode processor
exceptions by Intel.
Video cards suffered from their own incompatibilities. There was no
standard interface for using higher-resolution
SVGA graphics modes
supported by later video cards. Each manufacturer developed their own
methods of accessing the screen memory, including different mode
numberings and different bank switching arrangements. The latter were
used to address large images within a single 64kB segment of memory.
Previously, the VGA standard had used planar video memory arrangements
to the same effect, but this did not easily extend to the greater
colour depths and higher resolutions offered by
SVGA adapters. An
attempt at creating a standard named VESA
BIOS Extensions (VBE) was
made, but not all manufacturers used it.
When the 386 was introduced, again a protected mode OS could be
written for it. This time, DOS compatibility was much easier because
of virtual 8086 mode. Unfortunately programs could not switch directly
between them, so eventually, some new memory-model APIs were
VCPI and DPMI, the latter becoming the most popular.
Because of the great number of third-party adapters and no standard
for them, programming the PC could be difficult. Professional
developers would operate a large test-suite of various
known-to-be-popular hardware combinations.
Meanwhile, consumers were overwhelmed by the competing, incompatible
standards and many different combinations of hardware on offer. To
give them some idea of what sort of PC they would need to operate
their software, the
Multimedia PC (MPC) standard was set during 1990.
A PC that met the minimum MPC standard could be marketed with the MPC
logo, giving consumers an easy-to-understand specification to look
for. Software that could operate on the most minimally MPC-compliant
PC would be guaranteed[who?] to operate on any MPC. The MPC level 2
and MPC level 3 standards were set later, but the term "MPC compliant"
never became popular. After MPC level 3 during 1996, no further MPC
standards were established.
By the late 1990s, the success of
Microsoft Windows had driven rival
commercial operating systems into near-extinction, and had ensured
that the “IBM PC compatible” computer was the dominant computing
platform. This meant that if a developer made their software only for
Wintel platform, they would still be able to reach the vast
majority of computer users. By the late 1980s, the only major
competitor to Windows with more than a few percentage points of market
share was Apple Inc.'s Macintosh. The Mac started out billed as "the
computer for the rest of us" but the Mac's high prices and closed
architecture meant the DOS/Windows onslaught quickly drove the
Macintosh into an education and desktop publishing niche, from which
it only emerged in the mid-2000s. By the mid-1990s the Mac's market
share had dwindled to around 5% and introducing a new rival operating
system had become too risky a commercial venture. Experience had shown
that even if an operating system was technically superior to Windows,
it would be a failure in the market (
OS/2 for example). In
Steve Jobs said of his new
NeXT system, "It will either be the
last new hardware platform to succeed, or the first to fail." Four
years later in 1993
NeXT announced it was ending production of the
NeXTcube and porting
NeXTSTEP to Intel processors.
Very early on in PC history, some companies introduced their own
XT-compatible chipsets. For example,
Chips and Technologies
Chips and Technologies introduced
82C100 XT Controller which integrated and replaced six of the
original XT circuits: one
8237 DMA controller, one
8255 parallel interface controller, one
8284 clock generator, and one
8288 bus controller.
Similar non-Intel chipsets appeared for the AT-compatibles, for
example OPTi's 82C206 or 82C495XLC which were found in many 486 and
early Pentium systems. The x86 chipset market was very volatile
though. In 1993,
VLSI Technology had become the dominant market player
only to be virtually wiped out by Intel a year later. Intel has been
the uncontested leader ever since. As the "Wintel" platform gained
dominance Intel gradually abandoned the practice of licensing its
technologies to other chipset makers; in 2010 Intel was involved in
litigation related to their refusal to license their processor bus and
related technologies to other companies like Nvidia.
Companies such as
Cyrix developed alternative CPUs that were
functionally compatible with Intel's. Towards the end of the 1990s,
AMD was taking an increasing share of the CPU market for PCs.
ended up playing a significant role in directing the development of
the x86 platform when its Athlon line of processors continued to
develop the classic x86 architecture as Intel deviated with its
Netburst architecture for the Pentium 4 CPUs and the IA-64
architecture for the
Itanium set of server CPUs.
AMD developed AMD64,
the first major extension not created by Intel, which Intel later
adopted as x86-64. During 2006 Intel began abandoning
the release of their set of "Core" processors that represented a
development of the earlier Pentium III.
A major alternative to
Wintel domination is the rise of mobile
computing since the early 2000s, which has been marked as the start of
a post-PC era. By mid-2016, Windows-running PCs had a little less than
half the market share of all computers; but all such "IBM PC"
compatibles with the additional macOS-running computers, that are also
capable of running Windows, "PCs" had at that point a slight majority.
Mobile computers, running Android and iOS – Tablets and
smartphones – based on CPUs with the ARM architecture –
represent the bulk of personal computers "PCs", in that sense, while
not in the "IBM PC compatible" sense. A version of Windows, Windows RT
(that got discontinued, with later versions; namely
Windows 10 not
only supporting x86 but also), exists for ARM-based
IBM PC compatible
IBM PC compatible today
See also: Legacy-free PC
The term "IBM PC compatible" is not commonly used presently because
all current mainstream desktop and laptop computers are based on the
PC architecture, and IBM no longer makes PCs. The competing hardware
architectures have either been discontinued or, like the Amiga, have
been relegated to niche, enthusiast markets. In the past, the most
successful exception was Apple's
Macintosh platform, which used
non-Intel processors from its inception. Although
initially based on the Motorola 68000 family, then transitioned to the
Macintosh computers transitioned to Intel
processors beginning in 2006. Today's
Macintosh computers share the
same system architecture as their
Wintel counterparts and can boot
Microsoft Windows without delegating to a DOS Compatibility Card.
The processor speed and memory capacity of modern PCs are many orders
of magnitude greater than they were for the original IBM PC and yet
backwards compatibility has been largely maintained – a 32-bit
operating system released during the 2000s[update] can still operate
many of the simpler programs written for the OS of the early 1980s
without needing an emulator, though an emulator like
DOSBox now has
near-native functionality at full speed. Additionally, many modern PCs
can still run DOS directly, although special options such as USB
legacy mode and SATA-to-PATA emulation may need to be set in the BIOS
setup utility. Computers using the
Extensible Firmware Interface
Extensible Firmware Interface might
need to be set at legacy
BIOS mode to be able to boot DOS. However,
the BIOS/EFI options in most mass-produced consumer-grade computers
are very limited and cannot be configured to truly handle OSes such as
the original variants of DOS.
The recent spread of the x86-64 architecture has further distanced
current computers' and operating systems' internal similarity with the
original IBM PC by introducing yet another processor mode with an
instruction set modified for 64-bit addressing, but x86-64 capable
processors also retain standard x86 compatibility.
AT (form factor)
ATX form factor
Baby AT form factor
Custom built PC
History of computing hardware (1960s–present)
IBM Personal Computer
Influence of the IBM PC on the personal computer market
PS/2 - successor released by IBM that did not succeed, but many of its
elements have been adopted by industry
PC-9800 series - competing standard
PowerPC Reference Platform →
Common Hardware Reference Platform -
competing standard for PowerPC
^ Norton, Peter (5 February 1985). "Software for Once and All". PC
Magazine. p. 103. Retrieved 28 October 2013.
^ Libes, Sol (December 1981). "Bytelines". BYTE. pp. 314–318.
Retrieved 29 January 2015.
^ "Lookalikes From Home & Abroad". PC Magazine. February–March
1982. p. 5. Retrieved 20 October 2013.
^ Zussman, John Unger (1982-08-23). "Let's keep those systems open".
InfoWorld. p. 29. Retrieved 29 January 2015.
^ Sandler, Corey (June 1983). "Getting To Know You". PC Magazine.
p. 31. Retrieved 21 October 2013.
^ a b Mace, Scott (9–16 January 1984). "IBM PC clone makers shun
total compatibility". InfoWorld. pp. 79–81. Retrieved 4
^ Cook, Karen; Langdell, James (24 January 1984). "PC-Compatible
Portables". PC Magazine. p. 39. Retrieved 23 October 2013.
^ "Radio Shack Computer Catalog RSC-12, page 4". radioshackcatalogs
dot com. Tandy/Radio Shack. Retrieved June 27, 2017.
^ "Radio Shack Computer Catalog RSC-11, page 6". radioshackcatalogs
dot com. Tandy/Radio Shack. Retrieved June 27, 2017.
^ a b c Pournelle, Jerry (November 1984). "NCC Reflections". BYTE.
p. 361. Retrieved 23 October 2013.
^ Ward, Ronnie (November 1983). "Levels of PC Compatibility". BYTE.
pp. 248–249. Retrieved 19 March 2016.
^ a b Yakal, Kathy (January 1985). "
Bruce Artwick / The Designer
Behind Flight Simulator II". Compute!'s Gazette. p. 32. Retrieved
6 July 2014.
^ Alsop, Stewart (31 January 1994). "A public Windows pane to make
compatibility clearer". InfoWorld. p. 102. Retrieved 28 February
^ da Cruz, Frank (1984-01-23). "IBM PC Kermit". Info-Kermit Digest
(Mailing list). Kermit Project, Columbia University. Retrieved 23
^ Krasnoff, Barbara (20 March 1984). "No Matter Who's Invited, Some
Will Turn Out To Be Incompatible". PC Magazine. p. 57. Retrieved
24 October 2013.
^ Krasnoff, Barbara (3 April 1984). "Putting PC Compatibles To the
Test". PC Magazine. pp. 110–144. Retrieved 24 October
^ "Pick Up Where IBM Leaves Off".
1984-02-27. p. 41. Retrieved 18 January 2015.
^ Malloy, Rich (September 1983). "The Corona Portable PC". BYTE.
pp. 226–228. Retrieved 16 August 2015.
^ a b Pournelle, Jerry (July 1984). "The West Coast Faire". Byte.
p. 136. Retrieved November 8, 2011.
^ a b Lockwood, Russ (September 1985). "Zenith Z-151; choice of U.S.
Air Force and Navy". Creative Computing. p. 50. Retrieved 26
^ Poor, Alfred (2 October 1984). "Zenith Strikes Twice". PC Magazine.
p. 206. Retrieved 25 October 2013.
^ Callamaras, Peter V. (November 1984). "The Columbia Multipersonal
Computer-VP". BYTE. p. 276. Retrieved 23 October 2013.
^ Mace, Scott; Karen Sorensen (5 May 1986). "Amiga, Atari Ready PC
Emulators". InfoWorld. p. 5. Retrieved 28 February 2011.
^ Caruso, Denise (1984-02-27). "IBM wins disputes over PC copyrights".
InfoWorld. p. 15. Retrieved 18 January 2015.
^ Langdell, James (1984-07-10). "Phoenix Says Its
BIOS May Foil IBM's
Lawsuits". PC Magazine. p. 56. Retrieved 25 October 2013.
^ Schmidt, Robert (July 1994). "What Is The BIOS?". Computing Basics.
Archived from the original on 2012-03-10. Retrieved 2011-09-19.
^ "Competing on Price". InfoWorld. 1985-09-30. p. 1. Retrieved 20
^ Halfhill, Tom R. (December 1986). "The
MS-DOS Invasion / IBM
Compatibles Are Coming Home". Compute!. p. 32. Retrieved 9
^ Curran, Lawrence J. (Feb 1984). "The Compatibility Craze". BYTE.
p. 4. Retrieved 26 August 2015.
^ Machrone, Bill (26 November 1985). "Compatibility Wars—Here and
Abroad". PC Magazine. p. 59. Retrieved 29 October 2013.
^ Webster, Bruce (January 1987). "View and Reviews". Byte.
p. 367. Retrieved 4 November 2013.
^ Borrell, Jerry (May 1992). "Opening Pandora's Box". Macworld.
^ Parker, Rachel (1987-05-04). "PC Vendors' Sales Rise Following PS/2
Debut". InfoWorld. pp. 1,85.
^ a b c Scisco, Peter (December 1988). "Bus, Bus, Magic Bus".
Compute!. p. 10. Retrieved 10 November 2013.
^ LaPlante, Alice; Furger, Roberta (1989-01-23). "
Compaq Vying To
Become the IBM of the '90s". InfoWorld. pp. 1, 8. Retrieved 17
^ Reimer, Jeremy. "Total share: 30 years of personal computer market
share figures". Ars Technica. Retrieved 13 September 2008.
^ Miller, Michael. "Why The IBM PC Had An Open Architecture".
forwardthinking dot pcmag dot com. Ziff Davis. Retrieved June 27,
^ Brown, Marcel. "IBM Signs A Deal With The Devil".
thisdayintechhistory dot com. MB Tech, Inc. Retrieved June 27,
^ Killen, Michael (Fall 1984). "IBM Forecast / Market Dominance".
Byte. pp. 30–38. Retrieved 18 March 2016.
InfoWorld July 1986 ad: "Career Starter Kit: Everything you need to
begin serious computing immediately".
InfoWorld July 1986.
^ Mike Tooley (2005). PC Based Instrumentation and Control (3rd ed.).
Newness. p. 32. ISBN 978-1-136-37449-4.
^ Scott M. Mueller (2011). Upgrading and Repairing PCs (20th ed.). Que
Publishing. p. 171. ISBN 978-0-13-268218-3.
^ Intel vs. Nvidia: The tech beh