🚀 go-pugleaf

In comp.periphs.scsi 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?

<snip>

There are two important things to be aware of - one is the clock frequency
of the SCSI bus, the other is the width of the data path. So:-

'Normal' SCSI (SCSI 1) has a 5Mhz clock
Fast SCSI has a 10Mhz clock
Ultra SCSI has a 20Mhz clock

Narrow SCSI means an 8-bit data path
Wide SCSI means a 16-bit data path

So, an Ultra Wide device can do 16-bit transfers at 20Mhz, for a maximum
40Megabit/s transfer rate, while a Fast wide could only do 20 Megabits/second,
but an Ultra device (non-wide) could also manage 20 Megabits/second.

SCSI 1 was the original standard, and referred to 5Mhz 8-bit devices.
SCSI 2 encompasses several other options, up to (I think) 10Mhz 8-bit
devices. SCSI 3 is not yet an officially ratified standard.

HTH

Mike.