🚀 go-pugleaf

On Sun, 05 Oct 1997 22:32:22 -0700, Bryan Anderson <aced@swbell.net>
wrote:

>I have come across many terms that relate to SCSI. They are as follows:
>
>SCSI                SCSI 2                SCSI 3
>Fast SCSI         Fast SCSI 2        Fast SCSI 3
>Ultra SCSI        Ultra Fast SCSI
>Narrow SCSI    Wide SCSI
>
>I know that Narrow and Wide refer to 50-pin connection and 68-pin
>connection. But what do all the other terms mean? I have heard these

Technically, it refers to the bus width. Narrow = 8 bits. Wide = 16
bits. But yes, wide devices do have a different cable then narrow
ones.

>terms and others and I am getting confused as to what is what. I am new
>to SCSI, and any help that I can get will be appreciated. Can someone
>please explain these and other terms that are used for SCSI? Or point me
>towards a web site or two that will explain it? Any help will be

Its not that bad. 2 ways to push data faster: widen the bus and clock
it faster.

So. Original scsi had a clock rate (forget off the top of my head).
Fast SCSI protocol specified a clock 2x as fast, but with the same
narrow (8 bit) bus width. so, you get 10 Mb/s instead
of 5 Mb/s (this is total bus throughput of course).

So...now you can have a fast wide controller -> 20 Mb/s. Simple math
:)

Ultra scsi raises the clock speed again (2x) so an ultra wide
controller has a theoretical bus throughput of 40 Mb/s. (I am
not up on ultra scsi specs, so forgive an error here...I am
still happily stuck in the fast-wide world).


- b


Brian P. Van Lieu               
LU Ultimate Frisbee --- GOHO!    AXP-Phi Mu Chapter
95 Frost GSR Coupe, nothin' but G Stock
Visit the Integra homepage at http://integra.vtec.net

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