What interface is scsi?

scsi is the small computer system interface, the abbreviation of "Small Computer System Interface"; the interface is an independent processor standard for system-level interfaces between computers and peripheral devices, on the scsi bus Can connect host adapter and eight scsi peripheral controllers.

The operating environment of this tutorial: Windows 10 system, DELL G3 computer.

What is scsi interface

Small Computer System Interface (SCSI, Small Computer System Interface) is a type of interface used between computers and peripheral devices (hard disk, floppy drive, optical drive, Processor-independent standard for system-level interfaces (printers, scanners, etc.).

The SCSI standard defines commands, communication protocols, and electrical characteristics of entities (in OSI terms, it occupies the physical layer, link layer, socket layer, and application layer). The largest number of applications are in Storage devices (such as hard disks, tape drives); however, in fact, devices that can be connected to SCSI include scanners, optical devices (such as CDs, DVDs), printers, etc. The SCSI command lists the supported devices SCSI Peripherals. Theoretically, it is impossible for SCSI to connect all devices, so the parameter "1Fh - unknown or no device type" exists.

The SCSI interface is a universal interface. The host adapter and eight SCSI peripheral controllers can be connected to the SCSI bus. The peripherals can include disks, tapes, CD-ROMs, rewritable optical disk drives, printers, Scanners and communication equipment, etc.

SCSI is a multi-tasking interface with bus arbitration function. Multiple peripherals hanging on a SCSI bus can work simultaneously. Devices on SCSI share the bus equally.

The SCSI interface can transmit data synchronously or asynchronously. The synchronous transmission rate can reach 10MB/s, and the asynchronous transmission rate can reach 1.5MB/s.

When the SCSI interface is connected to an external device. Its connecting cable can be up to 6m long.

Type extension:

SCSI-1

SCSI-1 is the most original version, with asynchronous transmission frequency of 3MB/S and synchronous transmission frequency of 5MB/s. Although almost eliminated, it is still used in some scanners and internal ZIP drives, using a 25-pin interface. In other words, if you connect a SCSI-1 device to your SCSI card, you must have an internal 25- to 50-pin interface cable; if you use an external device, you cannot use any of the internal interfaces (that is, at this time None of the internal interfaces can be used).

SCSI-2

The early SCSI-2, called FastSCSI, increased the data transfer rate from the original 5MB/s to 10MB/s, supports 8-bit parallel data transmission, and can connect 7 peripherals. Later, WideSCSI supported 16-bit parallel data transmission, the data transmission rate was also increased to 20MB/s, and 16 peripherals could be connected. This version of SCSI uses a 50-pin interface and is mainly used in scanners, CD-ROM drives, and older hard disks.

SCSI-3

In 1995, a higher-speed SCSI-3 was born, called UltraSCSI, with a data transfer rate of 20MB/s. It increases the synchronous transmission clock frequency to 20MB/s, a technology that improves the data transfer rate. If you use the Wide mode of 16-bit transmission, the data transfer rate can be increased to 40MB/s. This version of SCSI uses a 68-pin interface and is mainly used on hard drives. The typical feature of SCSI-3 is to greatly increase the bus frequency and reduce signal interference to enhance its stability.

There are many models of SCSI-3. Ultra (fast-20) has a transmission frequency of 20MHz, a data bandwidth of 8 bits, and a transmission rate of 20MBps

Ultra wide has a transmission frequency of 20MHz and a data bandwidth of 16 bits, transmission rate 40MBps

Ultra 2 has a transmission frequency of 80MHz, data bandwidth is 16 bits, and transmission rate is 80MBps

Ultra 160 has a transmission frequency of 80MHz, data bandwidth is 16 bits, and transmission rate is 160MBps

Ultra 320 has a transmission frequency of 80MHz, a data bandwidth of 16 bits, and a transmission rate of 320MBps

Ultra 640 has a transmission frequency of 160MHz, a data bandwidth of 16 bits, and a transmission rate of 640MBps

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