Metal Male SCSI Cover Section

Small computer system interface (SCSI) is an independent processor standard for system level interfaces between computers and intelligent devices (hard disks, floppy drives, optical drives, printers, scanners, etc.). SCSI is an intelligent universal interface standard.

The maximum synchronous transmission rate of the original SCSI standard was 5MB / S (scsi-1, also known as narrowscsi, in 1986, the maximum support for seven devices, the clock frequency was 5MHz), and the later SCSI II specified two options for increasing the speed. One is to increase the frequency of data transmission, namely fast SCSI (in 1994, the maximum support for 7 devices) is 10 Mb / S (10 MHz) because the frequency is doubled; the other is to double the transmission frequency and increase the width of the data path from 8 bits to 16 bits. The maximum synchronous transmission speed of widescsi is 20MB / S (the clock frequency is 10MHz, in 1996, the maximum support for 15 devices).

The third generation of SCSI appeared around 1995, but there was no unified standard


1. Ultra SCSI with maximum synchronous transmission speed of 20MB / S (also known as FAST-20 SCSI, clock frequency of 20MHz);


2. Ultra wide SCSI with maximum synchronous transmission speed of 40MB / S (same as 1);

3. Ultra2 SCSI with maximum synchronous transmission speed of 40MB / S (also known as fast-40 SCSI, clock frequency of 40MHz, 1997).


Later, some newer SCSI standards appeared

1. Ultra2 widescsi with maxmum synchronous transmission speed of 80mb / S (clock frequency of 40MHz);

2. Ultra 3 SCSI with maximum synchronous transmission speed of 160MB / S (also known as ultra-160 or fast-80 wide SCSI, clock frequency of 40MHz plus double data rate, 1999);

3. Ultra 320 SCSI with maximum synchronous transmission speed of 320mb / S (also known as ultra 4 SCSI, clock frequency of 80MHz plus double data rate, 2002); 4. Ultra 640 SCSI with maximum synchronous transmission speed of 640MB / S (clock frequency of 160MHz plus double data rate, 2003, is the latest SCSI standard)

This interface is a convenient interface standard for system integration, cost reduction and efficiency improvement. More and more devices will use the SCSI interface standard. Therefore, there are many hard disks and SCSI CD-ROM drives with SCSI interface. However, due to the cost problem, they are mainly used on medium and high-end servers and workstations.