Adapter cards increase the functionality of a computer by adding controllers for specific devices or by replacing malfunctioning ports. Figure 1 shows several types of adapter cards, many of which can be integrated into the motherboard. These are some common adapter cards that are used to expand and customize the capability of a computer:
- Network Interface Card (NIC) - Connects a computer to a network using a network cable.
- Wireless NIC - Connects a computer to a network using radio frequencies.
- Sound adapter - Provides audio capability.
- Video adapter - Provides graphic capability.
- Capture card - Sends a video signal to a computer so that the signal can be recorded to the computer hard drive with Video Capture software.
- TV tuner card - Provides the ability to watch and record television signals on a PC by connecting a cable television, satellite, or antenna to the installed tuner card.
- Modem adapter - Connects a computer to the Internet using a phone line.
- Small Computer System Interface (SCSI) adapter - Connects SCSI devices, such as hard drives or tape drives, to a computer.
- Redundant Array of Independent Disks (RAID) adapter - Connects multiple hard drives to a computer to provide redundancy and to improve performance.
- Universal Serial Bus (USB) port - Connects a computer to peripheral devices.
- Parallel port - Connects a computer to peripheral devices.
- Serial port - Connects a computer to peripheral devices.
Computers have expansion slots on the motherboard to install adapter cards. The type of adapter card connector must match the expansion slot. The different types of expansion slots are shown in Figure 2.
A riser card was used in computer systems with the LPX form factor to allow adapter cards to be installed horizontally. The riser card was mainly used in slim-line desktop computers.
Communications and Networking Riser (CNR) is a special slot used for some networking or audio expansion cards. The CNR is not in use any more because many of the functions of the CNR are now found on-board the motherboard.