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Date: Thu, 29 Jan 2004 06:13:08 -0800 (PST)
From: Don Lewis <truckman@FreeBSD.org>
To: jesse@wingnet.net
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cc: freebsd-scsi@FreeBSD.org
Subject: Re: adaptec 2940u/uw dump card state ends
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On 29 Jan, Jesse Guardiani wrote:
> Don Lewis wrote:
> 
> 
> [...]
> 
>> My first guess would not be termination.  I would think that a
>> termination problem would muck up data transfers and would affect all
>> attempts to use the changer.
> 
> Well, it may be too soon to tell, but this past Monday (or maybe Sunday? I
> can't remember) the machine spontaneously rebooted on me during a backup
> cycle to the tape drive. It was midnight, but I decided to take a trip to
> the office and have a look at it anyway.
> 
> In the adaptec SCSI controller, I had the termination set to OFF for the LOW
> and HIGH parts of the bus. I changed this to AUTO for LOW and AUTO for HIGH
> and I turned off Ultra SCSI capability on the controller.
> 
> I'm not sure which of those changes fixed the problem, but so far - 3 or 4
> days later - I haven't seen a single timeout and no spontaneous reboots.
> 
> Hopefully it's fixed!
> 
> 

>> How is the changer connected to the 2940u/uw?  If you are using an eight
>> bit cable
> 
> Not sure what "bit" count it has, but it's an external wide cable. 50 pin,
> maybe?

That would be narrow/8-bit SCSI.  wide/16-bit SCSI uses a 68 pin cable.

>> you'll want to configure the 2940u/uw to terminate the upper
>> 8 bits of the bus but not the lower 8.
> 
> I think this may have been the problem. Setting both halves to "auto"
> probably fixed it.

If you previously had both upper and lower termination turned off on the
controller, the upper 8 bits of your SCSI bus were only terminated on
one end of the bus ...