Extended Industry Standard Architecture (EISA) is the extended PC bus based on Industry Standard Architecture (ISA). It was introduced in 1988 by well-known PC and chip manufacturers and works with 32 bits, but is compatible with the 16-bit architecture of the ISA.
EISA is suitable for the 32-bit CPUs 386 and 486, has a clock frequency of 8.33 MHz and a data transfer rate of 33 MB/s. The clock generator supplies the central processing unit (CPU) and, after frequency division, also the EISA bus. The EISA bus controller distinguishes ISAS and EISA bus signals and splits the 32-bit data units into 8 bits and 16 bits for the XT and AT peripherals. The EISA bus slot consists of two levels with a total of 188 contacts: Level 1 is for ISA and has 98 contacts; Level 2 has 90 contacts for EISA.