Small Computer System Interface

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Related to Small Computer System Interface: SCSI, Integrated Drive Electronics, Serial Attached SCSI

small computer system interface

[¦smȯl kəm¦pyüd·ər ‚sis·təm ′in·tər‚fās]
(computer science)
An interface standard or format for personal computers that allows the connection of up to seven peripheral devices. Abbreviated SCSI (scuzzy).

Small Computer System Interface

(hardware, standard)
(SCSI) /skuh'zee/, /sek'si/ The most popular processor-independent standard, via a parallel bus, for system-level interfacing between a computer and intelligent devices including hard disks, floppy disks, CD-ROM, printers, scanners, and many more.

SCSI can connect multiple devices to a single SCSI adaptor (or "host adaptor") on the computer's bus. SCSI transfers bits in parallel and can operate in either asynchronous or synchronous modes. The synchronous transfer rate is up to 5MB/s. There must be at least one target and one initiator on the SCSI bus.

SCSI connections normally use "single ended" drivers as opposed to differential drivers. Single ended SCSI can suport up to six metres of cable. Differential ended SCSI can support up to 25 metres of cable.

SCSI was developed by Shugart Associates, which later became Seagate. SCSI was originally called SASI for "Shugart Associates System Interface" before it became a standard.

Due to SCSI's inherent protocol flexibility, large support infrastructure, continued speed increases and the acceptance of SCSI Expanders in applications it is expected to hold its market.

The original standard is now called "SCSI-1" to distinguish it from SCSI-2 and SCSI-3 which include specifications of Wide SCSI (a 16-bit bus) and Fast SCSI (10 MB/s transfer).

SCSI-1 has been standardised as ANSI X3.131-1986 and ISO/IEC 9316.

A problem with SCSI is the large number of different connectors allowed. Nowadays the trend is toward a 68-pin miniature D-type or "high density" connector (HD68) for Wide SCSI and a 50-pin version of the same connector (HD50) for 8-bit SCSI (Type 1-4, pin pitch 1.27 mm x 2.45 mm). 50-pin ribbon cable connectors are also popular for internal wiring (Type 5, pin pitch 2.54 mm x 2.54 mm). Apple Computer used a 25-pin connector on the Macintosh computer but this connector causes problems with high-speed equipment. Original SCSI implementations were highly incompatible with each other.

ASPI is a standard Microsoft Windows interface to SCSI devices.

Usenet newsgroup: news:comp.periphs.scsi.

news:comp.periphs.scsi. SCSI Trade Association & FAQ

References in periodicals archive ?
End-user pricing for the external subsystem is $2,495 which includes a SCSI (Small Computer System Interface) card for IBM and compatible PCs.
FC offers three times the throughput of SCSI (Small Computer System Interface), improving overall data throughput and reducing the "backup windows" during which applications must be taken off-line to allow data to be backed up.
Under the terms of the partnership both companies will work together to deliver next-generation semiconductor solutions for gigabit ethernet and Internet small computer system interface (iSCSI) - a storage networking standard.
By now, you've undoubtedly heard of the Internet Small Computer System Interface (iSCSI), the emerging protocol standard that allows SCSI devices to interconnect over TCP/IP And when you think of iSCSI, your first reaction is an evolutionary technology that provides Ethernet ubiquity to Storage Area Networks (SANs) mid block capability to Network Attached Storage (NAS), both of which are true.
The Small Computer System Interface (SCSI) has been setting the standard for storage I/O for over 20 years.
The FC4 layer provides for ULP mapping, such as small computer system interface (SCSI), Internet protocol (IP), and virtual interface (VI).
So if you feel the need--the need for speed--look to the next generation of the small computer system interface, packetized SCSI.

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