An IBM PC compatible computer (also known as "IBM compatible", "PC clone" or simply "PC") is a computer designed to be, on a varying degree, software-compatible with International Business Machines's 1981 5150 Personal Computer. Like the original PC, most compatibles mount x86-compatible CPUs and run either a DOS-family operating system or a version of Microsoft Windows, although a large number of third-party OSes have started to circulate since PCs are available. One of the most notable of these system standards is the Unix-like OS Linux.
PCs have historically been pitted by the personal computer market against Apple, Inc.'s Macintosh computers, although Apple's 2009 decision to change the Macintosh architecture to a PC-like architecture has lowered the technical differences and made possible to turn PCs into "Hackintoshes" (unauthorized Mac-compatible systems).
This article will describe the common standards followed by PC-compatible system manufacturers.
CPU standards[]
PC-compatible computers usually mount x86 CPUs, which means they are compatible with the 1978 16-bit Intel 8086, a variant of which (the 8088) was mounted on the original IBM PC. The standard 8086s and 8088s were replaced by the Intel 80286 on the "286" variant of the IBM PC XT in 1983 and on the IBM PC AT in 1984. This CPU started the "286" standard, and a computer known as "a 286" mounted an 80286 or a compatible CPU, which could also be called as such. The replacement for the 286 standard was the IA-32 line of 32-bit processors, which included various different models, starting with the Intel 80386 (1985, first mounted on Compaq PCs, commencing with the 1986 Compaq Deskpro 386, rather than IBMs).
Graphics standards[]
PC-compatible computers usually followed precise standards for video and graphics, except for the first years, during which various incompatible standards were available on the market.
- MDA: a video card standard based on the IBM Monochrome Display Adapter card, which was available with the original PC. Monochrome high-resolution text mode only (25 x 80 columns).
- CGA: alternative to the MDA standard, based on the IBM Color Graphics Adapter card, also available with the PC. Three graphics modes (up to 16 colors) and two text modes. Allows for composite video output.
- HGC: a third-party standard developed by Hercules Computer Technology, Inc. for the 1982 Hercules Graphics Card, although also supported by the later Hercules Graphics Card Plus (HGC+, 1986) and Hercules InColor Card (1987).
- Tandy Graphics Adapter (TGA) or Tandy: a standard developed by Tandy Corporation for the Tandy Video I and Tandy Video II video cards to be compatible with the IBM PCjr's video standard. Released in 1984 with the Tandy 1000 series of PCs. The first video card was completely PCjr-compatible, with the same capabilities of the original (including some CGA compatibility modes), and was used on Tandy 1000s before the SL; the second one (which's standard was known as "ETGA") also added one more graphics mode (non CGA-compatible) to the PCjr's ones.
- PGC: a new standard based on the IBM Professional Graphics Controller card, available with the IBM PC XT in 1984. CGA compatibility plus a 640 x 680-pixels 256-colours mode, and a 4096-colours palette.
- EGA: a new standard developed by IBM for the IBM Enhanced Graphics Adapter card, released in 1984. CGA compatibility plus various graphics and text modes.
- JEGA:
- MCGA:
- VGA:
- 8514:
- SVGA:
- AX-VGA:
- TIGA:
- XGA: