Extended Industry Standard Architecture (in practice
almost always shortened to EISA and frequently pronounced "eee-suh") that extends the ISA
standard to a 32-bit interface. It was developed in part as an open alternative
to the proprietary "Micro Channel Architecture (MCA)" that IBM
introduced in its PS/2 computers. It 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 (MCA) in its PS/2
series.
EISA extends the AT bus, which the PC clone Vendors retroactively
renamed to the !SA bus to avoid infringing IBM's trademark on its PC/AT
computer, 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.
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 AlphaServer, HP 9000-D, SGI Indigo2 and MIPS
Magnum.
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