Although the EISA stands for Extended Industry Standard Architecture, it never really made it as an accepted architecture industry wide.
The original concept was a response to the IBM ‘MCA’ (Microchannel Architecture) bus which was a proprietary bus and offered the 32 bit wide path for the expansion bus.
The EISA was not a proprietary bus like the IBM MCA was, and it also offered backward compatibility to the 16 bit and the 8 bit ISA cards that were on the market during that time frame.
The key feature that permitted backward compatibility is that the 32 bit contacts are located deeper in the expansion slot.
Shallower 8/16 bit contacts allowed the backward compatibility to older 8/16 bit expansion cards.
Key features of the EISA bus:
8/16 bit ISA cards will work in EISA slots.
The EISA bus is a 32 bus.
The EISA bus did support Bus Mastering adapters for greater efficiency, including bus arbitration.
EISA automatically configured adapter cards, similar to the Plug and Play standards of modern systems.
Notice in the exhibit there are 3 slots on this particular motherboard. The 16 bit and the 32 bit expansion slots looked identical. The difference is that the 32 bit contacts are located deeper within the expansion slot.
