Adding Special Functions: Expansion Cards

Expansion cards are specialized printed circuit boards that add one or more features or functions to the basic set supplied by the motherboard. The most common expansion card in today's computers is the graphics controller that transfers images from the computer to a video display monitor, but many others are also available. Among many other things, an expansion card might contain a wireless network (Wi-Fi) interface, a higher-quality audio controller than the one on the motherboard, or a controller and connectors for additional inputs and outputs or hard drives.

The rear panel of the computer's case has a removable sheet metal cover over each expansion slot that keeps dust, fingers, and curious pets out of the case when no card is present. The sockets for expansion cards are connectors mounted on the motherboard that hold each card at right angles to the motherboard itself, with a sheet metal panel that replaces one of the removable covers. A machine screw attaches the cover or the back of the expansion card to the case.

Tip

Whenever you add an expansion card to your computer, it's a good idea to save the blank cover, just in case you ever remove the card.

The modular design of a PC makes the computer extremely flexible. It allows a user who needs some kind of specialized component to add that device on an expansion card without making the computer more complicated and more expensive for everybody else.

Interface types

The personal computer industry has used several standards for expansion cards. These standards specify the maximum dimensions, the number and arrangement of the electrical contacts on the surface that fit into a socket on the motherboard, and the signals supplied to each electrical contact. The sockets for different interfaces are not compatible with any other type, so each expansion card interface requires a matching slot on the motherboard.

Table 4.3 provides descriptions of the standard expansion card types used most often in desktop and tower computers.

Table 4.3: Motherboard Expansion Card Types
Open table as spreadsheet
Name	Description
ISA (Industry Standard Architecture)	Black sockets. General-purpose ISA cards are common in older PCs. More recent motherboards might have one or two ISA slots to allow old cards to work in a new computer, but for all practical purposes, ISA sockets are obsolete.
PCI (Peripheral Component Interconnect)	White sockets. PCI devices can transfer data ten times faster than ISA cards. Widely used in PCs and other platforms. Compatible with Plug and Play devices.
AGP (Accelerated Graphics Port)	Usually a brown socket. High-speed interface for graphic controllers (video cards). Most motherboards have one AGP socket, located closest to the CPU. PCI Express will eventually replace these on new motherboards.
PCI Express	Black sockets. Very high-speed replacement for PCI and AGP cards. Many new motherboards use PCI Express instead of AGP for graphics controllers.

Installing expansion cards

Before you install a new expansion card, confirm that the computer's power supply is rated for enough power to support the new card along with all the existing components. The computer's manual and the specification sheets for each disk drive, CD/DVD drive, and expansion card lists the number of watts that each device requires.

To add a new expansion card to your computer, follow these steps:

Unplug the AC power cable from the socket on the back of the computer.
Put an anti-static grounding strap on your wrist. Connect into the computer's case or other electrical ground, as described in the instructions supplied with the strap.
Remove the cover from the computer's case.
Find a socket that matches the type of card you want to install. For example, if your new gizmo is a PCI device, find an unused PCI socket. If it's an AGP or PCI Express graphics controller, find the AGP or PCI Express socket and remove the existing card, if any.
Use a ¼-inch nut driver or a screwdriver to remove the screw that holds the cover plate next to the socket to the back of the computer. Save the screw; you will need it to fasten the expansion card to the case.
Remove the cover plate and set it aside. If the cover doesn't fall off after you remove the screw, use a pair of long-nose pliers to pull it out. If necessary, loosen the screw on the next cover plate to make room for the one you want to remove.
Line up and insert the expansion card into the empty socket. Push it gently but firmly down into the motherboard to make sure the card is secure. If there's a latch holding the card into the socket, make sure it is engaged.
Use the screw you removed in Step 4 to attach the expansion card's backplate to the computer's case.
Follow the instructions supplied with the card to connect any additional wires.
Replace the cover onto the case.
Plug the power cable back into the socket on the back of the computer and turn it on.
When Windows starts, it might report that it has detected the new card and offer instructions for installing a device driver. Follow those instructions or the printed installation instructions supplied with the card instructions.