A printed circuit board that plugs into a slot on the motherboard and enables a computer to control a peripheral device. Also called an "interface card," "adapter" or "controller," all the printed circuit boards that plug into a computer's bus are technically expansion cards, because they "expand" the computer's capability.
They Used to Be the Norm
In earlier PCs, controllers for drives, input/output ports, display, network and sound all resided on separate plug-in cards. Subsequently, peripheral control was built into the chipset (see PC chipset
); however, users still have options to install their own controllers. For example, in order to enhance video game performance, a faster graphics card can be plugged into an empty PCI or PCI Express slot, and the internal display circuit on the motherboard can be disabled. See motherboard
and expansion port
. See also bus extender
Expansion cards come in many shapes and sizes, but they all conform to a specific pin format on the motherboard. This is a pile of graphics cards and Ethernet adapters with some sound boards thrown in for good measure. See PC data buses