Subject: Re: Dual SCSI, single chain?
To: Lindgren, Jon <>
From: Curt Sampson <>
List: port-alpha
Date: 03/28/1999 01:28:35
On Mon, 15 Mar 1999, der Mouse wrote:

> Um, if the "good" SCSI card is wide, its default ID will be 15, not 7.

No. All SCSI cards I've ever seen default to 7. They have to,
because otherwise they can't be `seen' by narrow drives.

> Termination might be a little tricky; the wide<->narrow adaptor will
> need to deal with this, and I don't know how good they are.

Termination shouldn't be a problem. You don't need to terminate
top and bottom halves in the same place. If you get a controller
with two ports it should be able to terminate top and bottom halves
independently (the Adaptec 2940 series can do this) and you can
just put the wide drive on one side and the narrow controller on
the other, properly terminating both ends, and terminating the top
half at the card. If you don't have such a wide controller, you
can buy a little `wide-to-narrow converter' to put in your SCSI
chain which will accept a wide connector, terminate the top 8 bits,
and give you a narrow SCSI connector coming out.

I don't really see any reason this shouldn't work, so long as the
narrow controller isn't configured into the kernel; once the kernel
loads and starts autoprobing the narrow controller should ignore
the SCSI bus entirely because no software has asked it to do
anything. Try it out and let us know how it goes.

Curt Sampson  <>   604 801 5335   De gustibus, aut bene aut nihil.
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