SCSI

Stands for "Small Computer System Interface," and is pronounced "scuzzy." SCSI is a computer interface used primarily for high-speed hard drives. This is because SCSI can support faster data transfer rates than the commonly used IDE storage interface. SCSI also supports daisy-chaining devices, which means several SCSI hard drives can be connected to single a SCSI interface, with little to no decrease in performance.

The different types of SCSI interfaces are listed below:

  • SCSI-1: Uses an 8-bit bus, supports data transfer speeds of 4 MBps.
  • SCSI-2: Uses a 50-pin connector instead of a 25-pin connector, and supports multiple devices. It is one of the most commonly used SCSI standards. Data transfer speeds are typically around 5 MBps.
  • Wide SCSI: Uses a wider cable (168 cable lines to 68 pins) to support 16-bit data transfers.
  • Fast SCSI: Uses an 8-bit bus, but doubles the clock rate to support data transfer speeds of 10 MBps.
  • Fast Wide SCSI: Uses a 16-bit bus and supports data transfer speeds of 20 MBps.
  • Ultra SCSI: Uses an 8-bit bus, supports data rates of 20 MBps.
  • SCSI-3: Uses a 16-bit bus, supports data rates of 40 MBps. Also called Ultra Wide SCSI.
  • Ultra2 SCSI: Uses an 8-bit bus, supports data transfer speeds of 40 MBps.
  • Wide Ultra2 SCSI: Uses a 16-bit bus, supports data transfer speeds of 80 MBps.
  • Ultra3 SCSI: Uses a 16-bit bus, supports data transfer rates of 160 MBps. Also known as Ultra-160.
  • Ultra-320 SCSI: Uses a 16-bit bus, supports data transfer speeds of 320 MBps.
  • Ultra-640 SCSI: Uses a 16-bit bus, supports data transfer speeds of 640 MBps.

While SCSI is still used for some high-performance equipment, newer interfaces have largely replaced SCSI in certain applications. For example, Firewire and USB 2.0 have become commonly used for connecting external hard drives. Serial ATA, or SATA, is now used as a fast interface for internal hard drives.

Updated November 1, 2007

Definitions by TechTerms.com

The definition of SCSI on this page is an original TechTerms.com definition. If you would like to reference this page or cite this definition, you can use the green citation links above.

The goal of TechTerms.com is to explain computer terminology in a way that is easy to understand. We strive for simplicity and accuracy with every definition we publish. If you have feedback about the SCSI definition or would like to suggest a new technical term, please contact us.

Want to learn more tech terms? Subscribe to the daily or weekly newsletter and get featured terms and quizzes delivered to your inbox.

Sign up for the free TechTerms Newsletter

How often would you like to receive an email?

You can unsubscribe or change your frequency setting at any time using the links available in each email.

Questions? Please contact us.