Chapter 11: Expansion Cards^223
was originally featured. Compare its edge connectors to those of the expansion
cards for the other expansion bus structures shown. On the motherboard, ISA
slots are typically black.
EISA (Extended ISA) The EISA (pronounced “ee-sa”) bus extended the
ISA bus to 32 bits and added bus mastering (see “Bus Mastering” later in the
chapter). EISA expansion slots are also backward compatible to ISA cards, with
a sectioned slot (shown in Figure 11-4) that support 8-bit and 16-bit ISA cards.
EISA has been replaced by the PCI bus (described next), but it is still available
on some motherboard designs. Like the ISA slots, EISA are black and are
placed next to the ISA slots on those motherboards that include them.
VESA local bus (VL bus) VL bus is a bus architecture developed by VESA
(Video Electronics Standards Association) for use with the 486 processor. A
local bus is one that is attached to the same bus structure used by the CPU. VL
bus is a 32-bit bus that supported bus mastering. The PCI bus has essentially
replaced the VL bus on modern PCs. If your PC has a VL bus expansion slot, it
is the one next to the ISA and EISA slots that has the extra slot added to the end
and is about four inches long in total. Figure 11-4 shows an illustrated view of
the relative size of the most common expansion slots.
PCI (Peripheral Component Interconnect) The PCI bus was introduced with
the first Intel Pentium computers and has become the de facto standard for
expansion cards on newer motherboards. The PCI bus is common on PCs,
Macintoshes, and high-end computer workstations. The PCI bus, which is a
local bus, typically supports devices mounted or connected directly to the
motherboard as well as in the PCI expansion slots. Most motherboards include
three or four of the white PCI expansion slots.Figure 11-3. A 16-bit ISA bus expansion card