System information

6-20
AlphaServer 800 Service Guide
6.3 EISA Bus Options
The EISA (Extended Industry Standard Architecture) bus is a 32-bit industry
standard I/O bus. EISA is a superset of the well-established ISA bus. EISA was
designed to accept newer 32-bit components while remaining compatible with older
8-bit and 16-bit cards.
The EISA bus is a superset of the well-established ISA bus and has been designed to
be backward compatible with 16-bit and 8-bit architecture. EISA offers performance
of up to 33 Mbytes/sec for bus masters and DMA devices.
Up to three EISA or ISA modules can be installed. If the 64-bit PCI slot is used,
only two EISA options can be installed. All slots are bus master slots. EISA slots
can be filled in any order.
WARNING: For protection against fire, only modules with current-limited outputs
should be used.
6.3.1 Identifying ISA and EISA Options
By examining the contacts of the option board you can determine whether a board is
EISA or ISA (Figure 6-4):
• ISA boards have one row of contacts and no more than one gap.
• EISA boards have two interlocking rows of contacts with several gaps.
Figure 6-4 EISA and ISA Boards
MA00111
ISA
EISA