An expansion board is an electronic circuit board that adds more functionality to a desktop computer. These cards are installed in the expansion slot on a computer’s motherboard and allow the computer to perform additional functions not provided by the motherboard. Video cards and sound cards are common examples: a new added video card will increase a computer’s 3D graphics processing power, while a new sound card can improve the computer’s audio input.
An expansion sound card can improve your computer’s audio input.
Alternative terms are used for this type of board, and it is also known as an expansion board, add-in board, interface adapter, or internal board. Typically, between one and seven expansion cards can be installed in the desktop computer system. Laptops do not use standard cards due to their small form factor, although they can accept a removable PCMCIA card that offers additional features.
Expansion cards, like graphics cards, can add functionality when plugged into the motherboard.
The Altair 8800, developed in the mid-1970s, was the first microcomputer to add an expansion board bus. In 1981, IBM® released its first PC with an XT bus, which was later replaced by a 16-bit ISA. The introduction of the PCI bus in 1991 resulted in modern forms of interface adapters that provided additional benefits beyond improved graphics and sound.
Most motherboards are inserted into PCI or “Peripheral Component Interconnect” slots, which are integrated circuits installed on the motherboard. An edge of the card containing the contacts or keys is inserted into the slot. This establishes electrical contact between the motherboard and the ICs on the board.
Standard interface adapters, such as video cards and sound cards, provide many additional features. Some video cards offer video capture, MPEG 2 and MPEG 4 decoding, a light pen, and the ability to connect to multiple monitors, for example. Sound cards can add features for composing music, editing audio presentations, and other multimedia applications.
There are some “low profile” boards that fit into a lower height computer frame. Some are used exclusively for external connectivity, such as modem cards, storage area network (SAN), and network cards, commonly called I/O cards or input/output cards. A USB card is mainly used by users who need additional USB or Firewire ports.
A PC expansion card can only be inserted into computers with available expansion slots. Computers such as the Apple Macintosh® and other all-in-one systems do not accept these cards.
Older computers require expansion cards to be connected via USB instead of the motherboard.
