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Date: Fri, 22 Mar 1996 16:27:50 +1000
From: George Scott <George.Scott@cc.monash.edu.au>
Subject: Re:  Crash advice needed (long) APPENDIX A
To: current@freebsd.org, hackers@freebsd.org
Cc: uhclem@nemesis.lonestar.org
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> sd0(aha0:0:0:) timed out:
> adapter not taking commands.. frozen?!
> Debugger("aha1542") called		(this system has a 1540B)
> AGAIN
> aha0: MBO 02 and not 00 (free)
> These last few lines repeat every ten seconds or so until I got
> tired of looking at them and pressed RESET.
> 
> (I have seen this MBO 02 and not 00 (free) message on a 1542C
>  controller at work when it is talking to a WangDat tape drive.
>  Sometimes this system also gets a "NO SENSE" message and
>  will claim the tape drive is not ready (it is ready) or busy (it isn't).
>  Solution on that system: turn everything off and back on and everyone
>  is happy.  Unfortunately, cycling power does not improve things here.)

I had this frequently under 2.1.0-RELEASE on a '486 with an AHA-1542CP (with
the P stuff disabled).

I had 5 drives on the external connector and 2 on the internal and noticed
that the time outs stopped happening when I disconnected either the external
or internal drives, so I figured bus length as the cause.  It was over 20'
so I shortened it as much as I could (to 16' if I remember) but the problems
still occured.

I ended up putting the internal drives on a spare AVA-1515 I had waiting for
another project and haven't had one problem since.

George.