The Industry Standard Architecture bus, used in IBM PC-Compatible systems, was first developed by IBM in 1981 for the IBM PC/XT. It was designed to accomadate system options, such as modems, disk controllers, and the like, that were not supported on the mainboard. At the time, it was an 8-bit bus, capable of maximum data transfer of approximately 2.4 Mbps.

With the release of the IBM PC/AT, the ISA bus was expanded to include the 16-bit functionality and 8 Mbps maximum data transfer rate present in that of modern PCs. A 32-bit extension, EISA, was implemented, but never gained much popularity.

Until 1993, when Plug and Play ISA was implemented, ISA cards had to be configured using jumpers on the board, or specialized programs, to set their IRQ, I/O Address, and DMA Channel. Plug and Play allowed these factors to be dynamically configured by the computer's operating system.

Many people believe that the ISA bus will be eventually supplanted entirely by the PCI bus. This seems to be borne out by the fact that more and more motherboards are being produced with only one or two ISA slots, and five or six PCI slots.

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The ISA bus has been supplanted by the PCI bus. Most motherboards today have no ISA slots at all, and there even exist motherboards with no legacy ports (PS/2 keyboard/mouse, serial, printer, etc.) at all (such as the abit AT7 MAX). While these motherboards still have a south bridge that provides an ISA bus, there is nothing connected to it, and no wires lead from it.

Such legacy free motherboards are becoming the norm, and it is likely that the with no call for legacy ports, the next generation of south bridges will not support the ISA bus at all.
