summary: Ultra narrow SCSI on a Fast narrow SCSI-2 bus

From: David W. Miles (sunspark@sun-valley.Stanford.EDU)
Date: Sat Dec 07 1996 - 08:45:20 CST

My original question was:

>I want to run an Artecon Lynx LX-2158UN drive, which is Ultra narrow
>SCSI, on our Sparc10 server, which has a fast SCSI-2 bus. Will this
>work? Will the drive default to the lower fast SCSI-2 rate? Are
>there any other considerations such as special cabling, termination,
>or drive ordering?

The summary is: Yes this will work fine. Other than keeping the SCSI
bus length short for ultra SCSI, there are no special considerations.

---- detailed answer 1 ----

This should work fine. The Sun SCSI driver should be smart enough
to lower the drives requested synchronous neogiation rate from 20MHz
(or whatever it asks for) to a maximum of 10MHz.

For normal (non-Ultra) transfers, there are no other considerations
you have to make. For Ultra transfers, you want to make the total
SCSI bus length as short as possible. I think the maximum bus length
for Ultra is half that of normal Fast SCSI-II.

Dan Eischen

---- detailed answer 2 ----

This should work. The SCSI specs have been very carefully written so that the
controller negotiates the maximum capability of the drives attached, including
slowing down if necessary to match.

Russ Poffenberger

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