by Paul Sanders
Your desktop computer's motherboard probably has one or more expansion card slots which you can use to add new functions, special connection ports, or powerful graphics capabilities to your computer. These expansion cards will increase the performance of your existing system.
Video graphics cards: In order to play advanced PC games, run high-definition movies, or use sophisticated image-editing software on your computer, you'll most likely need to boost the graphics processing power with a video card. Video cards take over processing 3D graphics and other video tasks, so your computer's CPU can focus on other functions.
SCSI controller: Your computer may not have the correct connection ports for connecting devices using the small computer system interface (SCSI), such as hard drives or certain high-speed scanners. An SCSI controller expansion card allows you to add a port for those devices.
RAID controller: A collection of hard drives connected in a RAID configuration can share or back up data in various ways, giving you options for backing up data or increasing storage over several drives. A RAID controller expansion card gives your computer ports for multiple hard drives through high-speed connections, usually SATA cables.
USB port card: Most desktops do have USB ports, but the version of USB they use may be too slow. You may also have more USB devices than you have ports. A multi-port USB expansion card adds high-speed ports to your computer that works faster than simple port-splitters. The latest version of USB is version 3.0, so any USB 3.0 card you install will be backwards compatible with your old USB devices and operate much faster than older ports.
TV tuner card: If you're setting up a home theater PC, you may want to be able to watch and record live TV broadcasts with a tuner card. Most tuner cards will include a coaxial cable connection to which you can attach an antenna or other video source. Some tuner cards will also be able to make recordings in multiple digital video formats.
Any expansion card needs to fit into a compatible slot on your motherboard, such as a PCI or PCI-Express slot. If your current system doesn't support the type of expansion card you want, you may be able to upgrade to a new motherboard with the proper interface slots.