Extended Industry Standard Architecture

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EISA Extended Industry Standard Architecture
Year Created:	1988
Created By:	Gang of Nine
Superseded By:	PCI (1993)
Width:	32 bits
Number of Devices:	1 per slot
Speed:	8.33 MHz
Style:	Parallel
Hotplugging?	No
External?	No

The Extended Industry Standard Architecture (in practice almost always shortened to EISA and frequently pronounced "eee-suh") is a bus standard for IBM compatible computers. It was announced in late 1988 by PC clone vendors (the "Gang of Nine") as a counter to IBM's use of its proprietary MicroChannel Architecture (MCA) 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 favoured by manufacturers due to the proprietary nature of MCA, and even IBM produced some machines supporting it. It was somewhat expensive to implement (though not as much as MCA), 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 (such as disk access and networking). 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.

By the time there was a strong market need for a bus of these speeds and capabilities, the VESA Local Bus and later PCI filled this niche and EISA vanished into obscurity.

[edit] Technical data

bus width	32 Bit
compatible with	8 bit ISA, 16 bit ISA, 32 bit EISA
pins	98 + 100 inlay
Vcc	+5 V, -5 V, +12 V, -12 V
clock	8.33 MHz
theoretical data rate (32 bit)	about 33 MByte/s [ 8.33 MHz * 4 bytes ]
usable data rate (32 bit)	about 20 MByte/s

[edit] See also

• Industry Standard Architecture (ISA)
• Micro Channel architecture (MCA)
• NuBus
• VESA Local Bus (VESA)
• Peripheral Component Interconnect (PCI)
• Accelerated Graphics Port (AGP)
• PCI Express (PCIe)

[edit] External links

• EISA bus technical summary
• "EISA System Architecture" published by Mindshare (pdf)
• Intel EISA Controllers

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	Preceding:	ISA
	Subsequent:	VESA Local Bus, MCA, PCI, PCI-X, PCI Express, PC/104, CompactPCI, PC card, LPC bus, Universal Serial Bus

This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.