What are Scsi Standards

[BADRU]

Hello , I am learning some old stuff related to computer hardware , can you tell me what are the scsi standards , and what do they define , please explain me the scsi standards in details , please help me thanks in advance

[deoWo]

SCSI standards define the electrical parameters of IO interfaces . The SCSI-1 standard was introduced in 1986, it defined the standard commands to control devices on a SCSI bus clocked at 4.77 MHz with a width of 8 bits, which allowed it to offer speeds of around 5 MB/s.

[Rawko]

In 1994 the SCSI-2 standard was adopted. It defines 18 commands called CCS (Common Command Set). Various versions of the standard SCSI-2 have been defined:

• The Wide SCSI-2 is based on a 16 bits bus width (instead of 8) and can provide a throughput of 10MB/s;
• The Fast SCSI-2 is a synchronous fast to go from 5 to 10 MB/s for the SCSI standard, and 10 to 20 Mb/s to the Wide SCSI-2
• Fast-20 and Fast-40 Modes respectively allow double and quadruple those rates.

[T.J.]

The SCSI standard 3 appeared in 1993, but it was officially recognized by ANSI in 1996 in the SCSI 3 Architecture Model SAM document under the name X3.270.1996. This standard includes several standards, and still not yet fully defined, It aims was to improve the performance of the SCSI bus, reliability, compatibility and support material and especially to allow a more flexible evolution of SCSI 3 , The standard SCSI-3 includes new orders, and allows the chaining of 32 devices and a maximum speed of 320 Mb / s (mode Ultra-320).