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Extended Industry Standard Architecture (EISA) is a bus architecture that extends the Industry Standard Architecture (ISA) from 16 bits to 32 bits. EISA was introduced in 1988 by the Gang of Nine – a group of PC manufacturers.
EISA was designed to compete with IBM’s Micro Channel Architecture (MCA) – a patented 16 and 32-bit parallel computer bus for IBM’s PS/2 computers. EISA extended the advanced technology (AT) bus architecture and facilitated bus sharing between multiple central processing units (CPU).
EISA is also known as Extended ISA.
Techopedia Explains Extended Industry Standard Architecture
The EISA bus is compatible with older ISA buses with 8-bit or 16-bit data paths. Two 32-bit data path slots are the same width as one 16-bit ISA slot. However, EISA bus slots are deeper than 16-bit slots because 32-bit circuit board edge connectors have long fingers deep inside the EISA slot that connect to the 32-bit pins. The 16-bit circuit board partly extends to the 16-bit pins with a shallow connection.
Enhanced 4 GB memory extended EISA’s 32-bit bus market, but the MCA bus was more popular. Though costly, EISA adapted easily to older ISA circuit boards. Thus, EISA was primarily used for high-end servers requiring heavy bandwidth. Unlike MCA, EISA accepts IBM’s older XT system architecture and ISA circuit boards. EISA connectors are 16-bit superset connectors for ISA system boards, providing more signals and enhanced performance.
The main difference between MCA and EISA is that EISA/ISA buses are backward compatible. An EISA PC is compatible with older EISA/ISA expansion cards, but on.ly MCA expansion cards may be used by an MCA bus.
EISA has 32-bit direct memory access (DMA), central processing unit (CPU) and bus master devices. EISA also has improved data transfer rates (DTR) up to 33 MB, automatic configuration, synchronous data transfer protocol (SDTP) and a compatible structure for older ISA buses with 8 or 16-bit data paths.
Most EISA cards were designed for network interface cards (NIC) or small computer system interfaces (SCSI). EISA is also accessible via several non IBM-compatible PCs, such as the HP 9000, MIPS Magnum, HP Alpha Server and SGI Indigo2.
Eventually, PCs required faster buses for higher performance. Faster expansion cards, like LocalBus or Video Electronics Standards Association (VESA), were introduced, and there was no longer an EISA card market.
