Small Computer System Interface

Abbreviated SCSI, which is pronounced "scuzzy."

A high-speed parallel interface defined by the ANSI X3T9.2 committee. SCSI is used to connect a computer to peripheral devices using only one port. Devices connected in this way are said to be "daisy-chained," and each device must have a unique identifier or priority number.

SCSI has been standard on the Macintosh since the Mac Plus was introduced, and it is available on personal computers as a single host adapter, using a special connector.

SCSI is often used to connect hard disks, tape drives, CD-ROM drives, and other mass storage media, as well as scanners and printers.

Features of the SCSI definition include:

• The bus can manage simultaneous reads and writes.
• The original standard supports as many as 7 devices on a single host adapter; new standards support as many as 16 devices and a bus length of up to 25 meters (80 feet).
• SCSI devices have their own control circuitry and can disconnect from the host adapter to process tasks on their own, freeing the bus for other purposes.

Table S.1 lists the various SCSI standards, along with the bus speed in Mbps, the bus width in bits, and the maximum number of devices supported.

See also Fast SCSI; Fast/Wide SCSI; SCSI-1; SCSI-2; SCSI-3; Ultra SCSI; Ultra2 SCSI; Wide Ultra SCSI; Wide Ultra2 SCSI.