IBM PC Compatible - Expandability

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 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.