Slots on the PC Motherboard

Bus and I/O Information for the various types of slots on personal computer motherboards.

ISA Bus (Industry Standard Architecture)

The first incarnation of this type of slot was the early 8-bit version called the XT bus. It was proprietary controlled by IBM. The original IBM Personal Computer introduced in 1981 included this 8-bit subset of the ISA bus.

In 1984, IBM introduced the PC-AT which was the first full 16-bit implementation of the ISA bus. The second incarnation was created by IBM called the AT bus, which was 16-bit and also proprietary at first. Due to a lack of industry specifications at first, not all of the original ISA bus devices were compatible and to this day no uniform standards has ever been set.

The ISA bus has enjoyed the longest run of any other card slot type. The ISA slot has since been abandoned in favor of more current technology.