Clone Pc Views

Software

When IBM announced the IBM PC in 1981, other companies such as Compaq decided to offer clones of the PC as a legal reimplementation from the PC's documentation or reverse engineering. Because most of the components, except the PC's BIOS, were publicly available, all Compaq had to do was reverse-engineer the BIOS. The result was a machine with better value than the archetypes that the machines resembled. The use of the term PC clone to describe IBM PC compatible computers fell out of use in the 1990s; the class of machines it now describes are simply called PCs.

While the term has fallen mostly into commercial disuse, the term clone for PCs still applies to a PC made to entry-level or above standard (at the time it was made) which bears no commercial branding (e.g., Acer, IBM, HP, Dell). This includes, but is not limited to, PCs assembled by home users or Corporate IT Departments. (See also White box (computer hardware).)

IBM PC compatible computers are those generally similar to the original IBM PC, XT, and AT. Such computers used to be referred to as PC clones, or IBM clones since they almost exactly duplicated all the significant features of the PC architecture, facilitated by various manufacturers' ability to legally reverse engineer the BIOS through clean room design. Columbia Data Products built the first clone of an IBM personal computer through a clean room implementation of its BIOS. Many 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 ISA bus by manufacturers of compatible computers. The term IBM PC compatible is now a historical description only since IBM has withdrawn from personal computer sales.

A number of computers of the time based on the 8086 and 8088 processors were manufactured during this period, but with different architecture to the PC, and which ran under their own versions of DOS and CP/M-86. However, software which addressed the hardware directly instead of making standard calls to MS-DOS was faster. This was particularly relevant to games. 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 functionally very similar to the PC. The 640 kB barrier on conventional system memory available to MS-DOS is a legacy of that period; other non-clone machines did not have this limit.