<hardware> (Or "host adaptor") A device that communicates between a computer and its SCSI peripherals. The SCSI adaptor is usually assigned SCSI ID 7. It is often a separate card that is connected to the computer's bus (e.g. PCI, ISA, PCMCIA) though increasinly, SCSI adaptors are built in to the motherboard. Apart from being cheaper, busses like PCI are too slow to keep up with the newer SCSI standards like Ultra SCSI and Ultra-Wide SCSI. There are several varieties of SCSI (and their connectors) and an adaptor will not support them all. The performance of SCSI devices is limited by the speed of the SCSI adaptor and its connection to the computer. An adaptor that plugs into a parallel port is unlikely to be as fast as one incorporated into a motherboard. Fast adaptors use DMA or bus mastering. Some SCSI adaptors include a BIOS to allow PCs to boot from a SCSI hard disk, if their own BIOS supports it. Adaptec make the majority of SCSI chipsets and many of the best-selling adaptors. Note that it is not a "SCSI controller" - it does not control the devices, and "SCSI interface" is redundant - the "I" of "SCSI" stands for "interface". (1999-11-24)

<hardware> A variant on the SCSI-2 bus. It uses the same 8-bit bus as the original SCSI-1 but runs at up to 10MB/s - double the speed of SCSI-1. (1994-11-24)

<hardware> A version of the SCSI command specification. SCSI-2 shares the original SCSI's asynchronous and synchronous modes and adds a "Fast SCSI" mode ( < 10MB/s ) and "Wide SCSI" (16 bit, < 20MB/s or rarely 32 bit). Another major enhancement was the definition of command sets for different device classes. SCSI-1 was rather minimalistic in this respect which led to various incompatibilities especially for devices other than hard-disks. SCSI-2 addresses that problem. allowing scanners, {hard disk drives}, CD-ROM drives, tapes and many other devices to be connected. Normal SCSI-2 equipment (not wide or differential) can be connected to a SCSI-1 bus and vice versa. (1995-04-19)

<hardware, standard> A variant on the SCSI-2 interface. It uses a 16-bit bus - double the width of the original SCSI-1 - and therefore cannot be connected to a SCSI-1 bus. It supports transfer rates up to 20 MB/s, like Fast SCSI. There is also a SCSI-2 definition of Wide-SCSI with a 32 bit data bus. This allows up to 40 megabytes per second but is very rarely used because it requires a large number of wires (118 wires on two connectors). Thus Wide SCSI usually means 16 bit-wide SCSI. (1995-04-21)

<hardware> The original SCSI, as opposed to SCSI-2 or SCSI-3. (1995-04-20)

<hardware> An ongoing standardisation effort to extend the capabilities of SCSI-2. SCSI-3's goals are more devices on a bus (up to 32); faster data transfer; greater distances between devices (longer cables); more device classes and command sets; structured documentation; and a structured protocol model. In SCSI-2, data transmission is parallel (8, 16 or 32 bit wide). This gets increasingly difficult with higher data rates and longer cables because of varying signal delays on different wires. Furthermore, wiring cost and drive power increases with wider data words and higher speed. This has triggered the move to serial interfacing in SCSI-3. By embedding clock information into a serial data stream signal delay problems are eliminated. Driving a single signal also consumes less driving power and reduces connector cost and size. To allow for backward compatibility and for added flexibility SCSI-3 allows the use of several different transport mechanisms, some serial and some parallel. The software protocol and command set is the same for each transport. This leads to a layered protocol definition similar to definitions found in networking. SCSI-3 is therefore in fact the sum of a number of separate standards which are defined by separate groups. These standards and groups are currently: X3T9.2/91-13R2 SCSI-3 Generic Packetized Protocol X3T9.2/92-141 SCSI-3 Queuing Model X3T9.2/92-079 SCSI-3 Architecture Model IEEE P1394 High Performance Serial Bus X3T9.2/92-106 SCSI-3 Block Commands X3T9.2/91-189 SCSI-3 Serial Bus Protocol X3T9.2/92-105 SCSI-3 SCSI-3 Core Commands SCSI-3 Common Command Set X3T9.2/92-108 SCSI-3 Graphic Commands X3T9.2/92-109 SCSI-3 Medium Changer Commands X3T9.2/91-11 SCSI-3 Interlocked Protocol X3T9.2/91-10 SCSI-3 Parallel Interface X3T9.2/92-107 SCSI-3 Stream Commands SCSI-3 Scanner Commands Additional Documents for the Fibre Channel are also meant to be included in the SCSI-3 framework, i.e.: Fibre Channel SCSI Mapping Fibre Channel Fabric Requirements Fibre Channel Low Cost Topologies X3T9.3/92-007 Fibre Channel Physical and Signalling Interface Fibre Channel Single Byte Commands Fibre Channel Cross Point Switch Topology X3T9.2/92-103 SCSI-3 Fibre Channel Protocol (GPP & SBP) As all of this is an ongoing effort of considerable complexity, document structure and workgroups may change. No final standard is issued yet. In the meantime a group of manufacturers have proposed an extension of SCSI-2 called Ultra-SCSI which doubles the transfer speed of Fast-SCSI to give 20MByte/s on an 8 bit connection and 40MByte/s on a 16-bit connection. [Hermann Strass: "SCSI-Bus erfolgreich anwenden", Franzis-Verlag Muenchen 1993]. (1995-04-19)

Parallel SCSI (formally, SCSI Parallel Interface, or SPI) is the earliest of the interface implementations in the SCSI family. SPI is a parallel bus; there is one set of electrical connections stretching from one end of the SCSI bus to the other.

In SCSI computer storage, computers and storage devices use a client-server model of communication. The computer is a client which requests the storage device to perform a service, e.

Signal transducing adaptor proteins (STAPs) are proteins that are accessory to main proteins in a signal transduction pathway. Adaptor proteins contain a variety of protein-binding modules that link protein-binding partners together and facilitate the creation of larger signaling complexes.

Clathrin adaptor proteins, also known as adaptins, are vesicular transport adaptor proteins associated with clathrin. These proteins are synthesized in the ribosomes, processed in the endoplasmic reticulum and transported from the Golgi apparatus to the trans-Golgi network, and from there via small carrier vesicles to their final destination compartment.