[ The PC Guide | Systems and Components Reference Guide | Hard Disk Drives | Hard Disk Interfaces and Configuration | Small Computer Systems Interface (SCSI) | SCSI Data Transfer Modes and Feature Sets ]

Wide Ultra SCSI

Description: Wide Ultra SCSI refers to devices that use 20 MHz SCSI bus speed on a wide, 16-bit bus, allowing for throughput of up to 40 MB/s. This is sometimes called Fast-20 Wide SCSI in reference to the Fast-20 signaling specification that defines Ultra SCSI speed. It is also sometimes called Ultra Wide SCSI.

Defining Standard: SCSI-3 / SPI (including Fast-20 addendum).

Special Features: None.

Bus Width: Wide (16-bit).

Signaling Method: SE or HVD.

Signaling Speed and Bus Throughput: 20 MHz bus speed; 40 MB/s.

Number of Devices Supported: 16 if HVD signaling is used; 8 if SE signaling is used with a maximum cable length of 1.5m; 4 if SE signaling is used with a cable length of over 1.5m.

Termination: For SE, either active or forced perfect termination. For HVD, HVD termination.

Cabling and Maximum Cable Length: "P" cable (68 pins). Maximum of 3m for SE if no more than 4 devices are used, otherwise 1.5m; 25m for HVD.

Next: Ultra2 SCSI

Home  -  Search  -  Topics  -  Up