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IBM PC compatible computers are similar to the original IBM PC, XT, and AT, all from computer giant IBM, that are able to use the same software and expansion cards. Such computers were referred to as PC clones, IBM clones or IBM PC clones. The term "IBM PC compatible" is now a historical description only, since IBM no longer sells personal computers after it sold its personal computer division in 2005 to Chinese technology company
Lenovo Lenovo Group Limited, often shortened to Lenovo ( , ), is a Chinese multinational technology company specializing in designing, manufacturing, and marketing consumer electronics, personal computers, software, business solutions, and related se ...
. The designation "PC", as used in much of personal computer history, has not meant "personal computer" generally, but rather an x86 computer capable of running the same software that a contemporary IBM PC could. The term was initially in contrast to the variety of home computer systems available in the early 1980s, such as the
Apple II The Apple II (stylized as ) is an 8-bit home computer and one of the world's first highly successful mass-produced microcomputer products. It was designed primarily by Steve Wozniak; Jerry Manock developed the design of Apple II's foam-mold ...
,
TRS-80 The TRS-80 Micro Computer System (TRS-80, later renamed the Model I to distinguish it from successors) is a desktop microcomputer launched in 1977 and sold by Tandy Corporation through their Radio Shack stores. The name is an abbreviation of ...
, and Commodore 64. Later, the term was primarily used in contrast to
Apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus '' Malus''. The tree originated in Central Asia, where its wild ances ...
's Macintosh computers. These "clones" duplicated almost all the significant features of the original IBM PC architectures. This was facilitated by IBM's choice of commodity hardware components, which were cheap, and by various manufacturers' ability to reverse-engineer the
BIOS In computing, BIOS (, ; Basic Input/Output System, also known as the System BIOS, ROM BIOS, BIOS ROM or PC BIOS) is firmware used to provide runtime services for operating systems and programs and to perform hardware initialization during the ...
firmware In computing, firmware is a specific class of computer software that provides the low-level control for a device's specific hardware. Firmware, such as the BIOS of a personal computer, may contain basic functions of a device, and may provide ...
using a " clean room design" technique. Columbia Data Products built the first clone of the IBM
personal computer A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or tech ...
, the MPC 1600 by a clean-room reverse-engineered implementation of its BIOS. Other rival companies, Corona Data Systems, Eagle Computer, and the Handwell Corporation were threatened with legal action by IBM, who settled with them. Soon after in 1982,
Compaq Compaq Computer Corporation (sometimes abbreviated to CQ prior to a 2007 rebranding) was an American information technology company founded in 1982 that developed, sold, and supported computers and related products and services. Compaq produced ...
released the very successful Compaq Portable in 1982, also with a clean-room reverse-engineered BIOS, and also not challenged legally by IBM. Some early IBM PC compatibles used the same
8-bit In computer architecture, 8-bit integers or other data units are those that are 8 bits wide (1 octet). Also, 8-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers or data buses of ...
computer bus as the original PC and XT models, but many soon adopted the 16-bit IBM AT bus. It was later re-named the Industry Standard Architecture (ISA) bus, after the Extended Industry Standard Architecture bus open standard for IBM PC compatibles was announced in September 1988 by a consortium of PC clone vendors, led by Compaq and called the Gang of Nine, as an alternative to IBM's proprietary Micro Channel architecture (MCA) introduced in its PS/2 series. Soon after the industry adopted new bus standards in a similar, cooperative way: the VESA Local Bus (VLB), Peripheral Component Interconnect (PCI) and the Accelerated Graphics Port (AGP). Descendants of the x86 IBM PC compatibles, namely 64-bit computers based on "
x86-64 x86-64 (also known as x64, x86_64, AMD64, and Intel 64) is a 64-bit version of the x86 instruction set, first released in 1999. It introduced two new modes of operation, 64-bit mode and compatibility mode, along with a new 4-level paging ...
/AMD64" chips comprise the majority of desktop computers on the market as of 2021, with the dominant
operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
being Microsoft Windows. Interoperability with the bus structure and peripherals of the original PC architecture may be limited or non-existent. Many modern computers are unable to use old software or hardware that depends on portions of the IBM PC compatible architecture which are missing or do not have equivalents in modern computers. For example, computers which boot using
Unified Extensible Firmware Interface UEFI (Unified Extensible Firmware Interface) is a set of specifications written by the UEFI Forum. They define the architecture of the platform firmware used for booting and its interface for interaction with the operating system. Examples ...
-based firmware that lack a Compatibility Support Module, or CSM, required to emulate the old BIOS-based firmware interface, or have their CSMs disabled, cannot natively run
MS-DOS MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few oper ...
since MS-DOS depends on a BIOS interface to boot. Only the Macintosh had kept significant market share without having compatibility with the IBM PC, although that changed with Intel Macs running Mac OS X, often dual-booting Windows with
Boot Camp Boot camp may refer to: Training programs * Boot camp (correctional), a type of correctional facility for adolescents, especially in the U.S. penal system * Boot camp, a training camp for learning various types of skills ** Dev bootcamp, a de ...
.


Origins

IBM decided in 1980 to market a low-cost single-user computer as quickly as possible. On 12 August 1981, the first IBM PC went on sale. There were three
operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
s (OS) available for it. The least expensive and most popular was PC DOS made by
Microsoft Microsoft Corporation is an American multinational corporation, multinational technology company, technology corporation producing Software, computer software, consumer electronics, personal computers, and related services headquartered at th ...
. In a crucial concession, IBM's agreement allowed Microsoft to sell its own version,
MS-DOS MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few oper ...
, for non-IBM computers. The only component of the original PC architecture exclusive to IBM was the
BIOS In computing, BIOS (, ; Basic Input/Output System, also known as the System BIOS, ROM BIOS, BIOS ROM or PC BIOS) is firmware used to provide runtime services for operating systems and programs and to perform hardware initialization during the ...
(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 to 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 on 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 that 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 By June 1983 '' PC Magazine'' defined "PC 'clone'" as "a computer hat canaccommodate 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 instead. 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 Compaq Computer Corporation (sometimes abbreviated to CQ prior to a 2007 rebranding) was an American information technology company founded in 1982 that developed, sold, and supported computers and related products and services. Compaq produced ...
announced its first product, an 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 court decision in '' Apple v. Franklin'', was that BIOS code was protected by copyright law, but it could reverse-engineer the IBM BIOS and then write its own BIOS using clean room design. Note this was over a year after Compaq released the Portable. The money and research put into reverse-engineering the BIOS was a calculated risk.


Compatibility issues


Non-compatible MS-DOS computers: Workalikes

At the same time, many manufacturers such as Tandy/ RadioShack,
Xerox Xerox Holdings Corporation (; also known simply as Xerox) is an American corporation that sells print and digital document products and services in more than 160 countries. Xerox is headquartered in Norwalk, Connecticut (having moved from St ...
, Hewlett-Packard,
Digital Equipment Corporation Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president unti ...
, Sanyo,
Texas Instruments Texas Instruments Incorporated (TI) is an American technology company headquartered in Dallas, Texas, that designs and manufactures semiconductors and various integrated circuits, which it sells to electronics designers and manufacturers globa ...
,
Tulip Tulips (''Tulipa'') are a genus of spring-blooming perennial herbaceous bulbiferous geophytes (having bulbs as storage organs). The flowers are usually large, showy and brightly coloured, generally red, pink, yellow, or white (usually in war ...
,
Wang Wang may refer to: Names * Wang (surname) (王), a common Chinese surname * Wāng (汪), a less common Chinese surname * Titles in Chinese nobility * A title in Korean nobility * A title in Mongolian nobility Places * Wang River in Thai ...
and
Olivetti Olivetti S.p.A. is an Italian manufacturer of computers, tablets, smartphones, printers and other such business products as calculators and fax machines. Headquartered in Ivrea, in the Metropolitan City of Turin, the company has been pa ...
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 PC-DOS programs did not work on 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 apparent 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 An original equipment manufacturer (OEM) is generally perceived as a company that produces non-aftermarket parts and equipment that may be marketed by another manufacturer. It is a common industry term recognized and used by many professional or ...
(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's business was based primarily on computer languages such as
BASIC BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Thomas E. Kurtz at Dartmouth College ...
. The established small system operating software was CP/M from
Digital Research Digital Research, Inc. (DR or DRI) was a company created by Gary Kildall to market and develop his CP/M operating system and related 8-bit, 16-bit and 32-bit systems like MP/M, Concurrent DOS, FlexOS, Multiuser DOS, DOS Plus, DR DOS ...
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 processor. Thus, 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 Trade dress is the characteristics of the visual appearance of a product or its packaging (or even the design of a building) that signify the source of the product to consumers. Trade dress is an aspect of trademark law, which is a form of intell ...
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 versions of 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 that MS-DOS supported directly.
Spreadsheet A spreadsheet is a computer application for computation, organization, analysis and storage of data in tabular form. Spreadsheets were developed as computerized analogs of paper accounting worksheets. The program operates on data entered in ce ...
s, WYSIWYG
word processor A word processor (WP) is a device or computer program that provides for input, editing, formatting, and output of text, often with some additional features. Word processor (electronic device), Early word processors were stand-alone devices ded ...
s, 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). While the 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
system call In computing, a system call (commonly abbreviated to syscall) is the programmatic way in which a computer program requests a service from the operating system on which it is executed. This may include hardware-related services (for example, acc ...
s.
Turbo Pascal Turbo Pascal is a software development system that includes a compiler and an integrated development environment (IDE) for the Pascal programming language running on CP/M, CP/M-86, and DOS. It was originally developed by Anders Hejlsberg at ...
used this technique from its earliest versions. * 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 BIOS interface 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 MS-DOS machine. *
Video game Video games, also known as computer games, are electronic games that involves interaction with a user interface or input device such as a joystick, game controller, controller, computer keyboard, keyboard, or motion sensing device to gener ...
s, 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, because the 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 19,200 bit/s. * Even for standard business applications, speed of execution was a significant competitive advantage. Integrated software Context MBA preceded
Lotus 1-2-3 Lotus 1-2-3 is a discontinued spreadsheet program from Lotus Software (later part of IBM). It was the first killer application of the IBM PC, was hugely popular in the 1980s, and significantly contributed to the success of IBM PC-compatible ...
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 DOS or 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.


First-generation PC workalikes by IBM competitors


"Operationally Compatible"

In May 1983, Future Computing defined four levels of compatibility: * ''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; (Good) Eagle. * ''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 Mate, Olivetti M20, Wang PC, Zenith Z-100. * ''Incompatible''. Cannot read PC disks. Can become Data Compatible. Examples: Altos 586, DEC Rainbow 100,
Grid Compass The Grid Compass (written ''GRiD'' by its manufacturer GRiD Systems Corporation) is one of the first laptop computers. History Development began in 1979, and the main buyer was the U.S. government. NASA used it on the Space Shuttle during th ...
, Victor 9000. During development, Compaq engineers found that '' Microsoft Flight 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 Computer hardware or software is said to be bug compatible if it exactly replicates even an undesirable feature of a previous version. The phrase is found in the Jargon File. An aspect of maintaining backward compatibility with an older system i ...
with the IBM PC. At first, few clones other than Compaq's offered truly full compatibility. Jerry Pournelle purchased an IBM PC in mid-1983, " rotten keyboard and all", because he had "four cubic feet of unevaluated software, much of which won't run on anything but an IBM PC. Although a lot of machines claim to be 100 percent IBM PC compatible, I've yet to have one arrive ... Alas, a lot of stuff doesn't run with Eagle, Z-100, Compupro, or anything else we have around here". Columbia Data Products's November 1983 sales brochure stated that during tests with retail-purchased computers in October 1983, its own and Compaq's products were compatible with all tested PC software, while Corona and Eagle's were less compatible.
Columbia University Columbia University (also known as Columbia, and officially as Columbia University in the City of New York) is a private research university in New York City. Established in 1754 as King's College on the grounds of Trinity Church in Manha ...
reported in January 1984 that Kermit ran without modification on Compaq and Columbia Data Products clones, but not on those from Eagle or Seequa. Other MS-DOS computers also required custom code. Future Computing said in February 1984 that some computers were "press-release compatible", exaggerating their actual compatibility with the IBM PC. Many companies were reluctant to have their products' PC compatibility tested. When ''PC Magazine'' requested samples from computer manufacturers that claimed to produce compatibles for an April 1984 review, 14 of 31 declined. 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 The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit ...
'' journalist asked to test
Peachtext Sage 50cloud is a set of Business software, accountancy and payroll products developed by Sage Group aimed at small and medium enterprises. Sage offer different products under the Sage 50 name in different regions. The product name originally deri ...
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 was bolder, bragging that its Z-150 ran all applications people brought to test with at the 1984 West Coast Computer Faire. ''
Creative Computing ''Creative Computing'' was one of the earliest magazines covering the microcomputer revolution. Published from October 1974 until December 1985, the magazine covered the spectrum of hobbyist/home/personal computing in a more accessible format th ...
'' 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. ''Apple Computer, Inc. v. Franklin Computer Corp.'', 714 F.2d 1240 (3d Cir. 1983), was the first time an appellate level court in the United States held that a computer's BIOS could be protected by copyright. As second impact, this ruling clarifie ...
'' successfully forced the clone makers to stop using the BIOS. The Phoenix BIOS in 1984, however, and similar products such as
AMI BIOS AMI (American Megatrends International LLC, formerly American Megatrends Inc.) is an international hardware and software company, specializing in PC hardware and firmware. The company was founded in 1985 by Pat Sarma and Subramonian Shankar. It ...
, 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 RAM, two disk drives, and monochrome monitors for to , while the equivalent IBM PC cost . The inexpensive Leading Edge Model D is even compatible with IBM proprietary diagnostic software, unlike the Compaq Portable. By 1986 '' Compute!'' stated that "clones are generally reliable and about 99 percent compatible", and a 1987 survey in the magazine of the clone industry did not mention software compatibility, stating that "PC by now has come to stand for a computer capable of running programs that are managed by MS-DOS".


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 ''
The Economist ''The Economist'' is a British weekly newspaper printed in demitab format and published digitally. It focuses on current affairs, international business, politics, technology, and culture. Based in London, the newspaper is owned by The Econ ...
'' stated in November 1983, "The main reason why an IBM standard is not worrying is that it can help competition to flourish". By 1983, IBM had about 25% of sales of personal computers between and , and computers with some PC compatibility were another 25%. As the market and competition grew IBM's influence diminished. In November 1985 ''PC Magazine'' stated "Now that it has created the Cmarket, 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, '' Macworld'' stated that because of clones, "IBM lost control of its own market and became a minor player with its own technology". ''The Economist'' predicted in 1983 that "IBM will soon be as much a prisoner of its standards as its competitors are", because "Once enough IBM machines have been bought, IBM cannot make sudden changes in their basic design; what might be useful for shedding competitors would shake off even more customers". After IBM announced the
OS/2 OS/2 (Operating System/2) is a series of computer operating systems, initially created by Microsoft and IBM under the leadership of IBM software designer Ed Iacobucci. As a result of a feud between the two companies over how to position 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 or superior. 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 Commodore Amiga line used for
television Television, sometimes shortened to TV, is a telecommunication Media (communication), medium for transmitting moving images and sound. The term can refer to a television set, or the medium of Transmission (telecommunications), television tra ...
and
video production Video production is the process of producing video content for video. It is the equivalent of filmmaking, but with video recorded either as analog signals on videotape, digitally in video tape or as computer files stored on optical discs, hard dri ...
and the 32-bit 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 MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few oper ...
, in order to offer PC compatibility for less cost. * The 1982 introduction of the Columbia Data Products MPC 1600, the first 100% IBM PC compatible computer. * The 1983 introduction of the Compaq Portable, providing portability unavailable from IBM at the time. * 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 decreasing margins. * The availability by 1986 of sub- "Turbo XT"
PC XT The IBM Personal Computer XT (model 5160, often shortened to PC/XT) is the second computer in the IBM Personal Computer line, released on March 8, 1983. Except for the addition of a built-in hard drive and extra expansion slots, it is very simila ...
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 The IBM Personal Computer/AT (model 5170, abbreviated as IBM AT or PC/AT) was released in 1984 as the fourth model in the IBM Personal Computer line, following the IBM PC/XT and its IBM Portable PC variant. It was designed around the Intel 8 ...
, and many companies did just that. * By integrating more peripherals into the computer itself, compatibles like the Model D have more free
ISA Isa or ISA may refer to: Places * Isa, Amur Oblast, Russia * Isa, Kagoshima, Japan * Isa, Nigeria * Isa District, Kagoshima, former district in Japan * Isa Town, middle class town located in Bahrain * Mount Isa, Queensland, Australia * Mount Is ...
slots than the PC. * Compaq was the first to release an Intel 80386-based computer, almost a year before IBM, with the Compaq Deskpro 386.
Bill Gates William Henry Gates III (born October 28, 1955) is an American business magnate and philanthropist. He is a co-founder of Microsoft, along with his late childhood friend Paul Allen. During his career at Microsoft, Gates held the positions ...
later said that it was "the first time people started to get a sense that it wasn't just IBM setting the standards". * IBM's 1987 introduction of the incompatible and proprietary MicroChannel Architecture (MCA) computer bus, for its
Personal System/2 The Personal System/2 or PS/2 is IBM's second generation of personal computers. Released in 1987, it officially replaced the IBM PC, XT, AT, and PC Convertible in IBM's lineup. Many of the PS/2's innovations, such as the 16550 UART (serial po ...
(PS/2) line. * The split of the IBM-Microsoft partnership in development of
OS/2 OS/2 (Operating System/2) is a series of computer operating systems, initially created by Microsoft and IBM under the leadership of IBM software designer Ed Iacobucci. As a result of a feud between the two companies over how to position OS/2 ...
. Tensions caused by the market success of Windows 3.0 ruptured the joint effort because IBM was committed to the 286's protected mode, which stunted OS/2's technical potential. Windows could take full advantage of the modern and increasingly affordable 386 / 386SX architecture. As well, there were cultural differences between the partners, and Windows was often bundled with new computers while OS/2 was only available for extra cost. The split left IBM the sole steward of OS/2 and it failed to keep pace with Windows. * 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 ( ThinkPad/
ThinkCentre The ThinkCentre is a line of business-oriented desktop computers designed, developed and marketed by Lenovo, and formerly by IBM from 2003 to 2005. ThinkCentre computers typically include mid-range to high-end processors, options for discrete ...
) to
Lenovo Lenovo Group Limited, often shortened to Lenovo ( , ), is a Chinese multinational technology company specializing in designing, manufacturing, and marketing consumer electronics, personal computers, software, business solutions, and related se ...
for . As of October 2007, Hewlett-Packard and
Dell Dell is an American based technology company. It develops, sells, repairs, and supports computers and related products and services. Dell is owned by its parent company, Dell Technologies. Dell sells personal computers (PCs), servers, data ...
had the largest shares of the PC market in North America. They were also successful overseas, with
Acer Acer may refer to: * ''Acer'' (plant), the genus of trees and shrubs commonly known as maples * Acer Inc., a computer company in Taiwan ** Acer Laboratories Incorporated, a subsidiary company of Acer, Inc., that designs and manufactures integrate ...
,
Lenovo Lenovo Group Limited, often shortened to Lenovo ( , ), is a Chinese multinational technology company specializing in designing, manufacturing, and marketing consumer electronics, personal computers, software, business solutions, and related se ...
, 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, the IBM PC compatibles remained 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 was often more practical to run old software on a modern system using an emulator rather than relying on these features. In 2014 Lenovo acquired IBM's x86-based server ( System x) business for .


Expandability

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 A motherboard (also called mainboard, main circuit board, mb, mboard, backplane board, base board, system board, logic board (only in Apple computers) or mobo) is the main printed circuit board (PCB) in general-purpose computers and other expand ...
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. "IBM PC compatible" becomes "Standard PC" in 1990s, and later " ACPI PC" in 2000s. 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 Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for ...
. In 1993, a version of
Windows NT Windows NT is a proprietary graphical operating system produced by Microsoft, the first version of which was released on July 27, 1993. It is a processor-independent, multiprocessing and multi-user operating system. The first version of Wi ...
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). 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 Microsoft could 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 hardware-software system. This terminology itself is becoming a misnomer, as Intel has lost absolute control over the direction of x86 hardware development with AMD's AMD64. Additionally, non-Windows operating systems like
macOS macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac (computer), Mac computers. Within the market of ...
and
Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which i ...
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 The Intel 8088 ("''eighty-eighty-eight''", also called iAPX 88) microprocessor is a variant of the Intel 8086. Introduced on June 1, 1979, the 8088 has an eight-bit external Bus (computing), data bus instead of the 16-bit computing, 16-bit bus of ...
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 ''PC''s beyond one megabyte, Lotus, Intel, and Microsoft jointly created expanded memory (EMS), a bank-switching scheme to allow more memory provided by add-in hardware, and accessed by a set of four 16- kilobyte "windows" inside the 20-bit addressing. Later, Intel CPUs had larger address spaces and could directly address 16 MB (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, bypassing BIOS routines intended to ensure compatibility, but also that most 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 64 KB 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 developed, 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 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.


Challenges to Wintel domination

By the late 1990s, the success of Microsoft Windows had driven rival commercial
operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
s 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 the Wintel platform, they would still be able to reach the vast majority of computer users. The only major competitor to Windows with more than a few percentage points of market share was
Apple, Inc. Apple Inc. is an American multinational technology company headquartered in Cupertino, California, United States. Apple is the largest technology company by revenue (totaling in 2021) and, as of June 2022, is the world's biggest company b ...
's Macintosh. The Mac started out billed as "the computer for the rest of us", but high prices and closed architecture 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 ( BeOS and
OS/2 OS/2 (Operating System/2) is a series of computer operating systems, initially created by Microsoft and IBM under the leadership of IBM software designer Ed Iacobucci. As a result of a feud between the two companies over how to position OS/2 ...
for example). In 1989,
Steve Jobs Steven Paul Jobs (February 24, 1955 – October 5, 2011) was an American entrepreneur, industrial designer, media proprietor, and investor. He was the co-founder, chairman, and CEO of Apple; the chairman and majority shareholder of Pixar; ...
said of his new
NeXT Next may refer to: Arts and entertainment Film * ''Next'' (1990 film), an animated short about William Shakespeare * ''Next'' (2007 film), a sci-fi film starring Nicolas Cage * '' Next: A Primer on Urban Painting'', a 2005 documentary film Lit ...
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 NeXTSTEP is a discontinued object-oriented, multitasking operating system based on the Mach kernel and the UNIX-derived BSD. It was developed by NeXT Computer in the late 1980s and early 1990s and was initially used for its range of proprieta ...
to Intel processors. Very early on in PC history, some companies introduced their own XT-compatible chipsets. For example, Chips and Technologies introduced their 82C100 XT Controller which integrated and replaced six of the original XT circuits: one
8237 Intel 8237 is a direct memory access (DMA) controller, a part of the MCS 85 microprocessor family. It enables data transfer between memory and the I/O with reduced load on the system's main processor by providing the memory with control signals ...
DMA controller, one 8253 interrupt timer, one 8255 parallel interface controller, one 8259 interrupt 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 Nvidia CorporationOfficially written as NVIDIA and stylized in its logo as VIDIA with the lowercase "n" the same height as the uppercase "VIDIA"; formerly stylized as VIDIA with a large italicized lowercase "n" on products from the mid 1990s to ...
.Intel vs. Nvidia: The tech behind the legal case
/ref> Companies such as AMD and Cyrix developed alternative x86 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. AMD even 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 x86-64 (also known as x64, x86_64, AMD64, and Intel 64) is a 64-bit version of the x86 instruction set, first released in 1999. It introduced two new modes of operation, 64-bit mode and compatibility mode, along with a new 4-level paging ...
. During 2006 Intel began abandoning Netburst with 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 alternative operating systems since the early 2000s, which has been marked as the start of a post-PC era.


The IBM PC compatible today

The term "IBM PC compatible" is not commonly used presently because many 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 An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus '' Malus''. The tree originated in Central Asia, where its wild ances ...
's Macintosh platform, which used non-Intel processors from its inception. Although Macintosh was initially based on the Motorola 68000 series, then transitioned to the
PowerPC PowerPC (with the backronym Performance Optimization With Enhanced RISC – Performance Computing, sometimes abbreviated as PPC) is a reduced instruction set computer (RISC) instruction set architecture (ISA) created by the 1991 Apple– IBM ...
architecture, Macintosh computers transitioned to Intel processors beginning in 2006. Until 2020 Macintosh computers shared the same system architecture as their Wintel counterparts and could boot Microsoft Windows without a DOS Compatibility Card. However, with the announcement of the internally developed ARM-based M1 CPU, they are again the exception to IBM compatibility. 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 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 (and is necessary for certain games which may run too fast on modern processors). 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
UEFI UEFI (Unified Extensible Firmware Interface) is a set of specifications written by the UEFI Forum. They define the architecture of the platform firmware used for booting and its interface for interaction with the operating system. Examples ...
might need to be set at legacy BIOS mode to be able to boot DOS. However, the BIOS/UEFI 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 spread of the
x86-64 x86-64 (also known as x64, x86_64, AMD64, and Intel 64) is a 64-bit version of the x86 instruction set, first released in 1999. It introduced two new modes of operation, 64-bit mode and compatibility mode, along with a new 4-level paging ...
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.


See also

* AT (form factor) * ATX form factor * Baby AT form factor *
BIOS In computing, BIOS (, ; Basic Input/Output System, also known as the System BIOS, ROM BIOS, BIOS ROM or PC BIOS) is firmware used to provide runtime services for operating systems and programs and to perform hardware initialization during the ...
* Computer hardware *
Computer software Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consists ...
* Computing platform * Custom-built PC * History of computing hardware (1960s–present) * Homebuilt computer *
IBM Personal Computer The IBM Personal Computer (model 5150, commonly known as the IBM PC) is the first microcomputer released in the IBM PC model line and the basis for the IBM PC compatible de facto standard. Released on August 12, 1981, it was created by a tea ...
*
Influence of the IBM PC on the personal computer market Following the introduction of the IBM Personal Computer, or IBM PC, many other personal computer architectures became extinct within just a few years. It led to a wave of IBM PC compatible systems being released. Before the IBM PC's introdu ...
* PC speaker *
Personal computer A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or tech ...
*
x86 architecture x86 (also known as 80x86 or the 8086 family) is a family of complex instruction set computer (CISC) instruction set architectures initially developed by Intel based on the Intel 8086 microprocessor and its 8088 variant. The 8086 was ...
*
MS-DOS MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few oper ...
* CP/M *
PS/2 The Personal System/2 or PS/2 is IBM's second generation of personal computers. Released in 1987, it officially replaced the IBM PC, XT, AT, and PC Convertible in IBM's lineup. Many of the PS/2's innovations, such as the 16550 UART (serial po ...
- successor released by IBM that did not succeed, but many of its elements have been adopted by industry *
PC-9800 series The , commonly shortened to PC-98 or , is a lineup of Japanese 16-bit and 32-bit personal computers manufactured by NEC from 1982 to 2000. The platform established NEC's dominance in the Japanese personal computer market, and, by 1999, more th ...
- competing standard * PowerPC Reference PlatformCommon Hardware Reference Platform - competing standard for PowerPC *
Unified Extensible Firmware Interface UEFI (Unified Extensible Firmware Interface) is a set of specifications written by the UEFI Forum. They define the architecture of the platform firmware used for booting and its interface for interaction with the operating system. Examples ...


References

{{DEFAULTSORT:Ibm Pc Compatible Computer-related introductions in 1982 * Computer hardware clones lt:PC