Small Computer System Interface
The Small Computer System Interface (universally known by its acronym, SCSI) was a popular interface standard for high-speed devices (disks, tape drives, scanners, etc). It was composed of a set of standards for the various layers: physical signalling, commands, etc.
Over time, a variety of options were developed for many of these; e.g. the original standard was 8-bit parallel using single-ended signalling, but later versions used 16-bit with differential pairs, at a variety of speeds (mostly synchronous, but one was asynchronous). Even later, a high-speed serial version was developed; and ultimately, one which worked over TCP/IP (usually over an Ethernet).
|Name||Alternative Name||max. Devices||Bus Bandwidth MB/sec|
|Fast(-Narrow) SCSI||(Narrow) SCSI-2||8||10|
|Fast-Wide SCSI||(Wide) SCSI-2||16||20|
|Ultra(-Wide) SCSI||(Wide) SCSI-3||16||40|