Datasheet

Input and Peripheral Devices 59
Adapter cards are purchased to match an available expansion slot in the motherboard.
PCI is the most common type of expansion slot for an adapter card in today’s PCs. ISA
slots are nearly obsolete, and AGP slots are used only for video cards.
Expansion slots are used to install various devices in the computer to expand its capa-
bilities. Some expansion devices that may be installed in these slots include video, network,
sound, and disk interface cards.
Expansion slots come in three main types: ISA, PCI, and AGP. Each type is different in
appearance and function, as you’ll learn in future chapters. You should be able to visually
identify the different expansion slots on the motherboard:
ISA Expansion Slots If you’re repairing a computer made before 1997, chances are the
motherboard in your computer has a few ISA slots. These slots are usually brown and are
separated into two unequal lengths. Computers made after 1997 generally include a few
ISA slots for backward compatibility with old expansion cards.
PCI Expansion Slots Most computers made today contain primarily PCI slots. They’re
easily recognizable, because they’re short (around 3 inches long) and are usually white. PCI
slots can usually be found in any computer that has a Pentium-class processor or higher.
AGP Expansion Slots AGP slots are very popular today. In the past, if you wanted to use a
high-speed, accelerated 3D graphics video card, you had to install the card into an existing PCI
or ISA slot. AGP slots were designed to be a direct connection between the video circuitry and
the PC’s memory. They’re also easily recognizable because they’re usually brown and located
right next to the PCI slots on the motherboard. Figure 1.22 shows an example of an AGP slot,
along with a PCI slot for comparison.
PCIE Expansion Slots PCIE combines the functionality of PCI with AGP and was dis-
cussed earlier in this chapter.
FIGURE 1.22 An AGP slot compared to a PCI slot
PCI slot
AGP slot
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