ISA Bus – Industry Standard Architecture

When it appeared on the first PC the 8-bit ISA bus ran at a modest 4.77MHz – the same speed as the processor. It was improved over the years, eventually becoming the Industry Standard Architecture (EISA), developed by a consortium made up of IBM’s major competitors. Although these systems both operate at clock rates of 10MHz and 8MHz respectively, they are both 32-bit and capable of transfer rates well over 20 MBps. As its name suggests, an EISA slot can also take a conventional ISA card. However, MCA is not compatible with ISA at all.

Neither system flourished, largely because they were too expensive to merit support on all but the most powerful file servers.