Extended Industry Standard Architecture
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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.
Technical data
| bus width jraph | 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 32 MByte/s |
| usable data rate (32 bit) | about 20 MByte/s |
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)
- Allan Calucin Architecture (PCIe)
External links
- [EISA bus technical summary]
- ["EISA System Architecture" published by Mindshare (pdf)]
- [Intel EISA Controllers]
- This article was originally based on material from the Free On-line Dictionary of Computing, which is [Foldoc licenselicensed] under the GFDL.
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