From owner-freebsd-hardware  Sun Nov  3 19:01:39 1996
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To: "Jordan K. Hubbard" <jkh@time.cdrom.com>
cc: hardware@freebsd.org
Subject: Re: OK, what's the deal with 2940W controllers and internal connectors? 
In-reply-to: Your message of "Sun, 03 Nov 1996 18:24:20 PST."
             <8387.847074260@time.cdrom.com> 
From: David Greenman <dg@root.com>
Reply-To: dg@root.com
Date: Sun, 03 Nov 1996 19:00:23 -0800
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>I just recently had a WIDE drive fall into my lap, so I finally
>started putting that WIDE connector on my 2940UW controller to good
>use.  While reading the Adaptec controller docs before jumping in, I
>saw that it very specifically said to use only ONE of the internal
>connectors, either the WIDE or the narrow, but not both.  You could
>still use the external connector for either kind of drive, but not
>hook both internal connectors up at once.  Well, this made sense to me
>since it seemed like otherwise you'd have a "Y" configuration in your
>SCSI bus, and it wasn't clear which devices you'd terminate if you
>plugged both internal connectors in - each end of the Y, or what?  So
>I hooked all my narrow devices to a 1542 controller I had lying around
>and life was good again, once I remembered to put BOUNCE_BUFFERS back
>in for it (feh).
>
>Then I was talking to Poul-Henning last night who pooh-pooh'd my
>foolish conservatism and stated that I could have used both internal
>connectors on my 2940UW no problem.  Since I could use that 1542 as my
>spare again (which is why I have it), I'd sort of like to know which
>one of us is correct? :-)

   You shouldn't have any trouble if you're only using the internal
connectors. There could be a problem with mixing the use of the external
connector and the internal connector that is on the same SCSI bus.

-DG

David Greenman
Core-team/Principal Architect, The FreeBSD Project