Extended Industry Standard Architecture
EISA was a motherboard slot type created by Compaq at 386 times in order to increase the performance of peripherals.
At that time, the most used slot type was ISA, which had a maximum theoretical transfer rate of 8 MB/s – too low even for a 386 (the maximum theoretical transfer rate of the external bus of a 386DX-33, for example, was 132 MB/s).
EISA was a 32-bit slot but, in order to be fully compatible with ISA (EISA slots allowed ISA cards to be installed) it still worked at 8 MHz. Because of that, its maximum theoretical transfer rate was of 16 MB/s. It doubled ISA performance, but it didn’t solve the problem.
EISA didn’t have large acceptance on the market and was found mainly on server motherboards.
Visually speaking, EISA slots are higher than ISA slots, and they are usually brown, while ISA slots are usually black.
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Figure 1: Motherboard with both EISA and ISA slots.