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SCSI
Small Computer System Interface (SCSI, /ˈskʌzi/ SKUZ-ee) is a set of standards for physically connecting and transferring data between computers and peripheral devices, best known for its use with storage devices such as hard disk drives. SCSI was introduced in the 1980s and has seen widespread use on servers and high-end workstations, with new SCSI standards being published as recently as SAS-4 in 2017.
The SCSI standards define commands, protocols, electrical, optical and logical interfaces. The SCSI standard defines command sets for specific peripheral device types; the presence of "unknown" as one of these types means that in theory it can be used as an interface to almost any device, but the standard is highly pragmatic and addressed toward commercial requirements. The initial Parallel SCSI was most commonly used for hard disk drives and tape drives, but it can connect a wide range of other devices, including scanners and optical disc drives, although not all controllers can handle all devices.
The ancestral SCSI standard, X3.131-1986, generally referred to as SCSI-1, was published by the X3T9 technical committee of the American National Standards Institute (ANSI) in 1986. SCSI-2 was published in August 1990 as X3.T9.2/86-109, with further revisions in 1994 and subsequent adoption of a multitude of interfaces. Further refinements have resulted in improvements in performance and support for ever-increasing data storage capacity.
SCSI is derived from the Shugart Associates System Interface (SASI), developed beginning 1979 and publicly disclosed in 1981. Larry Boucher is considered to be the "father" of SASI and ultimately SCSI due to his pioneering work first at Shugart Associates and then at Adaptec, which he founded in 1981.
A SASI controller provided a bridge between a hard disk drive's low-level interface and a host computer, which needed to read blocks of data. SASI controller boards were typically the size of a hard disk drive and were usually physically mounted to the drive's chassis. SASI, which was used in mini- and early microcomputers, defined the interface as using a 50-pin flat ribbon connector which was adopted as the SCSI-1 connector. SASI is a fully compliant subset of SCSI-1 so that many, if not all, of the then-existing SASI controllers were SCSI-1 compatible.
In around 1980, NCR Corporation had been developing a competing interface standard by the name of BYSE. In the summer of 1981, NCR abandoned their in-house efforts in favor of pursuing SASI and improving on its design for their own computer systems. Fearing that their extension of the SASI standard would induce market confusion, however, NCR briefly cancelled their contract with Shugart. NCR's proposed improvements to the design of SCSI piqued the interest of Optimem, a subsidiary of Shugart, who requested that NCR and Shugart collaborate on a unified standard. In October 1981, the two companies agreed to co-develop SASI and present their standard jointly with ANSI.
Until at least February 1982, ANSI developed the specification as "SASI" and "Shugart Associates System Interface". However, the committee documenting the standard would not allow it to be named after a company. Almost a full day was devoted to agreeing to name the standard "Small Computer System Interface", which Boucher intended to be pronounced "sexy", but ENDL's Dal Allan pronounced the new acronym as "scuzzy" and that stuck.
The NCR facility in Wichita, Kansas developed the industry's first SCSI controller chip, the NCR 5385, released in 1983. According to its developers, the chip worked the first time it was tested. A number of companies, such as Adaptec and Optimem, were early supporters of SCSI. By late 1990 at least 45 manufactures offered 251 models of parallel SCSI host adapters Today, such host adapters have largely been displaced by the faster serial SCSI (SAS) host adapters.
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SCSI
Small Computer System Interface (SCSI, /ˈskʌzi/ SKUZ-ee) is a set of standards for physically connecting and transferring data between computers and peripheral devices, best known for its use with storage devices such as hard disk drives. SCSI was introduced in the 1980s and has seen widespread use on servers and high-end workstations, with new SCSI standards being published as recently as SAS-4 in 2017.
The SCSI standards define commands, protocols, electrical, optical and logical interfaces. The SCSI standard defines command sets for specific peripheral device types; the presence of "unknown" as one of these types means that in theory it can be used as an interface to almost any device, but the standard is highly pragmatic and addressed toward commercial requirements. The initial Parallel SCSI was most commonly used for hard disk drives and tape drives, but it can connect a wide range of other devices, including scanners and optical disc drives, although not all controllers can handle all devices.
The ancestral SCSI standard, X3.131-1986, generally referred to as SCSI-1, was published by the X3T9 technical committee of the American National Standards Institute (ANSI) in 1986. SCSI-2 was published in August 1990 as X3.T9.2/86-109, with further revisions in 1994 and subsequent adoption of a multitude of interfaces. Further refinements have resulted in improvements in performance and support for ever-increasing data storage capacity.
SCSI is derived from the Shugart Associates System Interface (SASI), developed beginning 1979 and publicly disclosed in 1981. Larry Boucher is considered to be the "father" of SASI and ultimately SCSI due to his pioneering work first at Shugart Associates and then at Adaptec, which he founded in 1981.
A SASI controller provided a bridge between a hard disk drive's low-level interface and a host computer, which needed to read blocks of data. SASI controller boards were typically the size of a hard disk drive and were usually physically mounted to the drive's chassis. SASI, which was used in mini- and early microcomputers, defined the interface as using a 50-pin flat ribbon connector which was adopted as the SCSI-1 connector. SASI is a fully compliant subset of SCSI-1 so that many, if not all, of the then-existing SASI controllers were SCSI-1 compatible.
In around 1980, NCR Corporation had been developing a competing interface standard by the name of BYSE. In the summer of 1981, NCR abandoned their in-house efforts in favor of pursuing SASI and improving on its design for their own computer systems. Fearing that their extension of the SASI standard would induce market confusion, however, NCR briefly cancelled their contract with Shugart. NCR's proposed improvements to the design of SCSI piqued the interest of Optimem, a subsidiary of Shugart, who requested that NCR and Shugart collaborate on a unified standard. In October 1981, the two companies agreed to co-develop SASI and present their standard jointly with ANSI.
Until at least February 1982, ANSI developed the specification as "SASI" and "Shugart Associates System Interface". However, the committee documenting the standard would not allow it to be named after a company. Almost a full day was devoted to agreeing to name the standard "Small Computer System Interface", which Boucher intended to be pronounced "sexy", but ENDL's Dal Allan pronounced the new acronym as "scuzzy" and that stuck.
The NCR facility in Wichita, Kansas developed the industry's first SCSI controller chip, the NCR 5385, released in 1983. According to its developers, the chip worked the first time it was tested. A number of companies, such as Adaptec and Optimem, were early supporters of SCSI. By late 1990 at least 45 manufactures offered 251 models of parallel SCSI host adapters Today, such host adapters have largely been displaced by the faster serial SCSI (SAS) host adapters.