SCSI (pronounced scuzzy) is short for Small Computer System Interface, and the SCSI card controls various SCSI devices. SCSI devices might be hard drives, optical drives, scanners or tape drives.

A SCSI card is inserted into a PCI slot inside the computer. SCSI is a competing technology to the more standard IDE (Integrated Drive Electronics). Most hard disks are IDE, but the IDE controller card is integrated into the motherboard. If SCSI components are desired, a SCSI card is required.

There are various versions of the SCSI card that feature different connectors as the technology has evolved.

• 25-pin SCSI card controls original SCSI devices
• 50-pin SCSI card controls Narrow (8-bit) SCSI-2, FastSCSI, and Ultra SCSI devices
• 68-pin SCSI card controls Wide (16-bit) Ultra-Wide, Ultra2, Ultra 160, and Ultra 320 devices

Many people prefer SCSI to standard IDE as SCSI technology is much faster. SCSI drives are popular in servers and among power users. A SCSI card has its own processing chip and does not need to rely on the CPU (Central Processing Unit). The trade-off is that SCSI devices are more expensive than IDE devices. For this reason, many people opt to buy and use IDE hard drives, but will install a SCSI card for a SCSI DVD burner. The added speed of SCSI is useful for the demanding needs of burning and playing CDs and DVDs.

A great advantage of a SCSI card is that it can link up to 15 devices per card. This configuration is called daisy chaining and each device on the SCSI cable is assigned its own ID. The ability to add on to the SCSI card provides great flexibility for a RAID (Redundant Array of Independent Disks). If considering SCSI for a RAID, another viable alternative is a SATA (Serial ATA) RAID. SATA hard drives will be less expensive than SCSI drives, and the latest SATA drives should be comparable in speed to a SCSI Ultra 160 RAID or better.

SCSI cards are available everywhere computer components are sold. When purchasing a SCSI card, be sure it is compatible with the SCSI components you wish to purchase. SCSI devices generally carry a longer warranty than IDE devices, and SCSI drives are designed to work 24/7, catering to the server market.