Subject: Re: NCR Driver Problems
To: None <se@zpr.uni-koeln.DE>
From: Christoph Badura <>
List: current-users
Date: 01/24/1996 02:10:00
Stefan Esser wrote:
>There is one new explanation for your problems,
>which was found by somebody doing extensive tests
>under FreeBSD. Seems that the generic SCSI code 
>may cause problems with certain drives !

>A few drives seem to strongly dislike
>this command [start unit], after they once received a command
>with a tag!

>It is well possible, that it fully supports tags. 
>It is just picky about non-tagged commands (even
>NOP commands) sent when any tagged command is 

And it has every right to do so:

SCSI-2 7.8: " An initiator may not mix the use of tagged and untagged
queuing for I/O processes to a logical unit, except during a
contingent allegiance or extended contingend allegiance condition ..."

7.8.2:  "An I/O process received without a queue tag message, while
there are any tagged I/O commands in the command queue from the same
initiator, is an incorrect initiator connection (see 7.5.2), unless
there is a contingent allegiance or extended contingent allegiance

The same holds when a target receives a tagged command while a
untagged command from the same initiator is in its command queue.

I figure the problem isn't with the generic SCSI code but with your
driver violating the standard.

Christoph Badura

You don't need to quote my .signature.  Everyone has seen it by now.
Besides, it doesn't add anything to the current thread.