What is SCSI?
SCSI (Small Computer System Interface) is a set of ANSI standards for connecting computer systems and devices. The vast majority of SCSI devices are used for data storage.
Although standard SCSI is a parallel technology, many serial SCSI variants exist, including FireWire and Fibre Channel.
SCSI is generally considered a higher-end alternative to ATA. A single ATA controller can control two drives. A single SCI controller can control 8 or 16 drives. In addition, SCSI usually offers greater cable length and higher length than ATA.
SCSI Standards
| SCSI Standard | Cable Length | Speed (MBps) | Devices Supported |
|---|
| SCSI-1 | 6 | 5 | 8 |
| SCSI-2 | 6 | 5-10 | 8 or 16 |
| Fast SCSI-2 | 3 | 10-20 | 8 |
| Wide SCSI-2 | 3 | 20 | 16 |
| Fast Wide SCSI-2 | 3 | 20 | 16 |
| Ultra SCSI-3,8-bit | 1.5 | 20 | 8 |
| Ultra SCSI-3,16-bit | 1.5 | 40 | 16 |
| Ultra-2 SCSI | 12 | 40 | 8 |
| Wide Ultra-2 SCSI | 12 | 80 | 16 |
| Ultra-3 (Ultra160/m) SCSI | 12 | 160 | 16 |
Wide and Narrow SCSI
Many SCSI standards have options for Wide or Narrow operation. Wide SCSI is parallel SCI which transmits 16 bits of data at a time. Narrow SCSI is parallel SCSI which transmits 8 bits of data at a time.
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