SCSI is an acronym for Small Computer Systems Interface which basically attaches peripheral devices such as mouse, keyboard and printer to a computer, to transfer data simultaneously. These parallel interfaces are developed at Apple Computer and used in the Macintosh’s. SCSI ports are built into many personal computers and these are supported by all major operating systems.
The number of devices will depend on the bus width allowing up to 7 or 15 devices to be connected to single SCSI port.
Different SCSI are implemented and they are:
SCSI-1: Uses an 8-bit bus, and supports data rates of 4 MBps.
SCSI-2 (plain SCSI): Same as SCSI-1, but uses a 50-pin connector instead of a 25-pin connector, and supports multiple devices.
SCSI-3(Ultra Wide SCSI): Uses a 16-bit bus and supports data rates of 40 MBps.
Ultra2 SCSI: Uses an 8-bit bus and supports data rates of 40 MBps. It sends signals over two wires with data represented as the difference in voltage between the two wires. This allows support for longer cables.
Wide Ultra2 SCSI: Uses a 16-bit bus and supports data rates of 80 MBps.