SCSI

SASISmall Computer System InterfaceShugart Associates System InterfaceSCSI over PCI ExpressUltra3 SCSIFast 20 UltraSCSISCSI adapterSCSI controllersSCSI ExpressSCSI U320
Small Computer System Interface (SCSI, ) is a set of standards for physically connecting and transferring data between computers and peripheral devices.wikipedia
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SCSI command

commandcommandsSCSI command set
The SCSI standards define commands, protocols, electrical, optical and logical interfaces.
In SCSI computer storage, computers and storage devices use a client-server model of communication.

Tape drive

tape drivestapetape backup
SCSI is most commonly used for hard disk drives and tape drives, but it can connect a wide range of other devices, including scanners and CD drives, although not all controllers can handle all devices.
Tape drives can be connected to a computer with SCSI, Fibre Channel, SATA, USB, FireWire, FICON, or other interfaces.

Interface (computing)

interfaceinterfacescomputer interface
The SCSI standards define commands, protocols, electrical, optical and logical interfaces.
A standard interface, such as SCSI, decouples the design and introduction of computing hardware, such as I/O devices, from the design and introduction of other components of a computing system, thereby allowing users and manufacturers great flexibility in the implementation of computing systems.

Hard disk drive

hard drivehard diskhard drives
SCSI is most commonly used for hard disk drives and tape drives, but it can connect a wide range of other devices, including scanners and CD drives, although not all controllers can handle all devices.
Many Macintosh computers made between 1986 and 1998 featured a SCSI port on the back, making external expansion simple.

SCSI Peripheral Device Type

peripheral device typesSCSI processor device
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.
A SCSI Peripheral Device Type describes the capabilities provided by a SCSI device.

Parallel SCSI

SCSI-1SCSI-2SCSI
Recent physical versions of SCSISerial Attached SCSI (SAS), SCSI-over-Fibre Channel Protocol (FCP), and USB Attached SCSI (UAS)break from the traditional parallel SCSI bus and perform data transfer via serial communications using point-to-point links. The first was parallel SCSI (also called SCSI Parallel Interface or SPI), which uses a parallel bus design.
Parallel SCSI (formally, SCSI Parallel Interface, or SPI) is the earliest of the interface implementations in the SCSI family.

Fibre Channel Protocol

FCPFC0 and FC1 layers
Recent physical versions of SCSISerial Attached SCSI (SAS), SCSI-over-Fibre Channel Protocol (FCP), and USB Attached SCSI (UAS)break from the traditional parallel SCSI bus and perform data transfer via serial communications using point-to-point links. Fibre Channel can be used to transport SCSI information units, as defined by the Fibre Channel Protocol for SCSI (FCP).

Serial ATA

SATAeSATAmSATA
Sun switched its lower-end range to Serial ATA (SATA).
As with many other industry compatibility standards, the SATA content ownership is transferred to other industry bodies: primarily INCITS T13 and an INCITS T10 subcommittee (SCSI), a subgroup of T10 responsible for Serial Attached SCSI (SAS).

IEEE 1394

FireWireFireWire 400FireWire 800
Apple dropped on-board SCSI completely in favor of IDE and FireWire with the (Blue & White) Power Mac G3 in 1999, while still offering a PCI SCSI host adapter as an option on up to the Power Macintosh G4 (AGP Graphics) models.
Apple intended FireWire to be a serial replacement for the parallel SCSI bus, while providing connectivity for digital audio and video equipment.

Parallel ATA

IDEATAPATA
Apple started using the less-expensive parallel ATA (PATA, also known as IDE) for its low-end machines with the Macintosh Quadra 630 in 1994, and added it to its high-end desktops starting with the Power Macintosh G3 in 1997.
SCSI was available as a CD-ROM expansion option at the time, but devices with SCSI were more expensive than ATA devices due to the need for a smart interface that is capable of bus arbitration.

ISCSI

iSCSI target Internet SCSIInternet SCSI
The non-physical iSCSI preserves the basic SCSI paradigm, especially the command set, almost unchanged, through embedding of SCSI-3 over TCP/IP.
It provides block-level access to storage devices by carrying SCSI commands over a TCP/IP network.

USB Attached SCSI

UAS
Recent physical versions of SCSISerial Attached SCSI (SAS), SCSI-over-Fibre Channel Protocol (FCP), and USB Attached SCSI (UAS)break from the traditional parallel SCSI bus and perform data transfer via serial communications using point-to-point links.
UAS depends on the USB protocol, and uses the standard SCSI command set.

Atari Falcon

FalconFalcon030Atari Falcon030
Atari included SCSI as standard in its Atari MEGA STE, Atari TT and Atari Falcon computer models.
The Falcon Mk X was mounted in a 19" 1U rack case, with external keyboard and space for internal SCSI hard disk drives.

Macintosh

Apple MacintoshMacMacs
Since its standardization in 1986, SCSI has been commonly used in the Amiga, Atari, Apple Macintosh and Sun Microsystems computer lines and PC server systems.
It also featured a SCSI parallel interface, allowing up to seven peripherals—such as hard drives and scanners—to be attached to the machine.

NCR Corporation

NCRNational Cash RegisterNational Cash Register Company
A number of companies such as NCR Corporation, Adaptec and Optimem were early supporters of SCSI.
The majority of the System 3000 range utilised IBM's Micro Channel architecture rather than the more prevalent ISA architecture, and utilised SCSI peripherals as well as the more popular parallel and serial port interfaces, resulting in a premium product with premium pricing.

Bus (computing)

buscomputer busdata bus
Recent physical versions of SCSISerial Attached SCSI (SAS), SCSI-over-Fibre Channel Protocol (FCP), and USB Attached SCSI (UAS)break from the traditional parallel SCSI bus and perform data transfer via serial communications using point-to-point links. The first was parallel SCSI (also called SCSI Parallel Interface or SPI), which uses a parallel bus design.
Other common categorization systems are based on the bus's primary role, connecting devices internally or externally, PCI vs. SCSI for instance.

SCSI architectural model

SAM-4
Many other interfaces which do not rely on complete SCSI standards still implement the SCSI command protocol; others drop physical implementation entirely while retaining the SCSI architectural model.
The SCSI architectural model provides an abstract view of the way that SCSI devices communicate.

Shugart Associates

ShugartShugart Associates SA1000
SCSI is derived from "SASI", the "Shugart Associates System Interface", developed circa 1978 and publicly disclosed in 1981.
In 1979, Shugart Associates introduced the "Shugart Associates System Interface" (SASI) to the computing world; the interface subsequently evolved into SCSI (Small Computer System Interface).

Optical disc drive

optical driveCD driveDVD drive
SCSI is most commonly used for hard disk drives and tape drives, but it can connect a wide range of other devices, including scanners and CD drives, although not all controllers can handle all devices.
Drives with SCSI interface were made, but they are less common and tend to be more expensive, because of the cost of their interface chipsets, more complex SCSI connectors, and small volume of sales.

Atari TT030

Atari TTTTAtari System V
Atari included SCSI as standard in its Atari MEGA STE, Atari TT and Atari Falcon computer models.
For example, an AppleTalk network port (there never was a driver for it, possibly due to license problems), VME expansion bus, new VGA video graphics modes, and a true SCSI port.

Adaptec

Adaptec UK
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.
Adaptec produced interface products involving SCSI, USB, IEEE 1394, iSCSI, Fibre Channel, and video.

CD-ROM

CDCD-ROM driveCD-ROM XA
SCSI is most commonly used for hard disk drives and tape drives, but it can connect a wide range of other devices, including scanners and CD drives, although not all controllers can handle all devices.
A CD-ROM drive may be connected to the computer via an IDE (ATA), SCSI, SATA, FireWire, or USB interface or a proprietary interface, such as the Panasonic CD interface, LMSI/Philips, Sony and Mitsumi standards.

Fibre Channel

FCFiber Channel10GFC
Fibre Channel can be used to transport SCSI information units, as defined by the Fibre Channel Protocol for SCSI (FCP).
Fibre Channel Protocol (FCP) is a protocol that transports SCSI commands over Fibre Channel networks.

Conventional PCI

PCIPCI busPeripheral Component Interconnect
Apple dropped on-board SCSI completely in favor of IDE and FireWire with the (Blue & White) Power Mac G3 in 1999, while still offering a PCI SCSI host adapter as an option on up to the Power Macintosh G4 (AGP Graphics) models.
An example of this is the Adaptec 29160 64-bit SCSI interface card.

Parallel communication

parallelparallel busparallel transmission
The first was parallel SCSI (also called SCSI Parallel Interface or SPI), which uses a parallel bus design.