Expansion cards

The expansion card (also expansion board, adapter card or accessory card) in computing is a printed circuit board that can be inserted into an expansion slot of a computer motherboard or backplane to add functionality to a computer system via the expansion bus.
One edge of the expansion card holds the contacts (the edge connector) that fit exactly into the slot. They establish the electrical contact between the electronics (mostly integrated circuits) on the card and on the motherboard.

ISA SCSI card As can be seen by the below illustration, this adapter would enable users to connect Internal and external SCSI drives into their computers.

AGP - Accelerated Graphics Port, AGP is an advanced port designed for Video cards and 3D accelerators. Designed by Intel and introduced in August of 1997, AGP introduces a dedicated point-to-point channel that allows the graphics controller direct access the system memory. Below is an illustration of what the AGP slot may look like on your motherboard.

The AGP channel is 32-bits wide and runs at 66 MHz. This translates into a total bandwidth of 266 MBps, which is much greater than the PCI bandwidth of up to 133 MBps. AGP also supports two optional faster modes, with throughput of 533 MBps and 1.07 GBps. It also allows 3-D textures to be stored in main memory rather than video memory.

MR is short for Audio/Modem Riser and allows OEMs to make one card that has the functionality of either Modem or Audio or both Audio and Modem on one card. This specification allows for the motherboard to be manufactured at a lower cost and free up industry standard expansion slots in the system for other additional plug-in peripherals. In the picture to the right, is an example of what the AMR slot looks like on the Motherboard. This slot is often on the far edge of the motherboard, next to a PCI slot.

PCI

Peripheral Component Interconnect, PCI was introduced by Intel in 1992, revised in 1993 to version 2.0, and later revised in 1995 to PCI 2.1 and is as an expansion to the ISA bus. The PCI bus is a 32-bit computer bus that is also available as a 64-bit bus and was the most commonly found and used computer bus in computers during the late 1990's and early 2000's. Today's computers have replace PCI with PCI-Express. Below is a graphic illustration of the PCI slot on a motherboard.

Examples of PCI devices

Modem
Network card
Sound card
Video card

Modem

1. Short for MODulator/DEModulator, the first Modem was first released by AT&T in 1960 when it introduced its dataphone. The Modem is a hardware device that enables a computer to send and receive information over telephone lines. The Modem is responsible for converting the digital data used by your computer into an analog signal used on phone lines and then converting it back once received on the other end. In the picture to the right, is a UsRobotics 56k external Faxmodem, an example of what an external dial-up Modem looks like.

NIC/LAN Card

Short for Network Interface Card, a NIC is also commonly referred to as an Ethernet card and network adapter and is an expansion card that enables a computer to connect to a network such as a home network or the Internet using an Ethernet cable with a RJ-45 connector. In the picture to the right, is an example of a SMC EZ Card 10/100 PCI network card, a network card commonly found in most desktop computers today that do not already have an integrated network on their motherboard.

Sound card

Alternatively referred to as a sound board or an audio card, a sound card is an expansion card or integrated circuit that provides a computer with the ability to produce sounds that can be heard by the user either over speakers or headphones. Below is an image of the Creative Sound Blaster X-Fi Xtreme Audio sound card and an example of what a sound card may look like.

Audio-in connection on the back of a computer sound card

Video card

Alternatively referred to as a graphics card, video adapter, video board, or a video controller, a video card is an internal circuit board that allows a display device such as a monitor to display images from the computer. Today's video cards are most commonly connected to the AGP, PCI, or PCIe expansion slot on the motherboard, however, can also be found on-board.