Ultra SCSI, or FAST-20, is an emerging high-performance SCSI standard which began as an offshoot of the SCSI-2 command set, and is also incorporated in the SCSI-3 parallel command set. Ultra SCSI effectively doubles the maximum transfer rates provided under Fast SCSI-2 to up to 20MB per second on an 8-bit bus and up to 40MB per second on a 16-bit bus (called Ultra Wide). Its terrific performance specifications make Ultra SCSI an attractive data storage and retrieval system for high-end servers and workstations.