The Extended Industry Standard Architecture

The Extended Industry Standard Architecture is a bus standard for IBM compatible computers. It was announced in late 1988 by PC clone vendors as a counter to IBM's use of its proprietary Micro Channel Architecture in its PS/2 series. EISA extends the ISA bus architecture to 32 bits and allows more than one CPU to share the bus. The bus mastering support is also enhanced to provide access to 4 GB of memory. Unlike MCA, EISA can accept older XT and ISA boards — the lines and slots for EISA are a superset of ISA.

Although somewhat inferior to MCA, EISA was much favored by manufacturers due to the proprietary nature of MCA, and even IBM produced some machines supporting it. It was somewhat expensive to implement, so it never became particularly popular in desktop PCs. However, it was reasonably successful in the server market, as it was better suited to bandwidth-intensive tasks. Most EISA cards produced were either SCSI or network cards. EISA was also available on some non-IBM compatible machines such as the Alpha Server, HP 9000-D, SGI.