page_title: History of personal computers
section_title: IBM PC clones
hierarchical_section_title: History of personal computers / The IBM PC / IBM PC clones
caption_attribution_description: English: Hewlett-Packard HP Vectra 286/12 PC, CPU: Intel 286 - 16 bit - 12 MHz -, 5,25 inch floppy disk drive, max 1 MByte RAM, HP A4032A 17 inch CRT, Operating System: Microsoft MS-DOS 6.0.
context_page_description: The history of the personal computer as a mass-market consumer electronic device began with the microcomputer revolution of the 1970s. A personal computer is one intended for interactive individual use, as opposed to a mainframe computer where the end user's requests are filtered through operating staff, or a time-sharing system in which one large processor is shared by many individuals. After the development of the microprocessor, individual personal computers were low enough in cost that they eventually became affordable consumer goods. Early personal computers – generally called microcomputers – were sold often in electronic kit form and in limited numbers, and were of interest mostly to hobbyists and technicians.
context_section_description: The original PC design was followed up in 1983 by the IBM PC XT, which was an incrementally improved design; it omitted support for the cassette, had more card slots, and was available with a 10MB hard drive. Although mandatory at first, the hard drive was later made an option and a two floppy disk XT was sold. While the architectural memory limit of 640K was the same, later versions were more readily expandable.
  Although the PC and XT included a version of the BASIC language in read-only memory, most were purchased with disk drives and run with an operating system; three operating systems were initially announced with the PC. One was CP/M-86 from Digital Research, the second was PC DOS from IBM, and the third was the UCSD p-System (from the University of California at San Diego). PC DOS was the IBM branded version of an operating system from Microsoft, previously best known for supplying BASIC language systems to computer hardware companies. When sold by Microsoft, PC DOS was called MS-DOS. The UCSD p-System OS was built around the Pascal programming language and was not marketed to the same niche as IBM's customers. Neither the p-System nor CP/M-86 was a commercial success.
  Because MS-DOS was available as a separate product, some companies attempted to make computers available which could run MS-DOS and programs. These early machines, including the ACT Apricot, the DEC Rainbow 100, the Hewlett-Packard HP-150, the Seequa Chameleon and many others were not especially successful, as they required a customized version of MS-DOS, and could not run programs designed specifically for IBM's hardware. (See List of early non-IBM-PC-compatible PCs.)
  The first truly IBM PC compatible machines came from Compaq, although others soon followed.
  Because the IBM PC was based on relatively standard integrated circuits, and the basic card-slot design was not patented, the key portion of that hardware was actually the BIOS software embedded in read-only memory. This critical element got reverse engineered, and that opened the floodgates to the market for IBM PC imitators, which were dubbed "PC clones". At the time that IBM had decided to enter the personal computer market in response to Apple's early success, IBM was the giant of the computer industry and was expected to crush Apple's market share. But because of these shortcuts that IBM took to enter the market quickly, they ended up releasing a product that was easily copied by other manufacturers using off the shelf, non-proprietary parts. So in the long run, IBM's biggest role in the evolution of the personal computer was to establish the de facto standard for hardware architecture amongst a wide range of manufacturers. IBM's pricing was undercut to the point where IBM was no longer the significant force in development, leaving only the PC standard they had established. Emerging as the dominant force from this battle amongst hardware manufacturers who were vying for market share was the software company Microsoft that provided the operating system and utilities to all PCs across the board, whether authentic IBM machines or the PC clones.
  In 1984, IBM introduced the IBM Personal Computer/AT (more often called the PC/AT or AT) built around the Intel 80286 microprocessor. This chip was much faster, and could address up to 16MB of RAM but only in a mode that largely broke compatibility with the earlier 8086 and 8088. In particular, the MS-DOS operating system was not able to take advantage of this capability.
  The bus in the PC/AT was given the name Industry Standard Architecture (ISA). Peripheral Component Interconnect (PCI) was released in 1992, and was supposed to replace ISA.
  VESA Local Bus (VLB) and Extended ISA were also displaced by PCI, but a majority of later (post-1992) 486-based systems were featuring a VESA Local Bus video card. VLB importantly offered a less costly high speed interface for consumer systems, as only by 1994 was PCI commonly available outside of the server market.
  PCI is later replaced by PCI-E (see below).
caption: HP Vectra 286/12 PC, IBM PC compatible computer with Intel 80286 processor
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