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From: Steve Passe <smp@csn.net>
To: "Louis A. Mamakos" <louie@TransSys.COM>
cc: multimedia@freebsd.org
Subject: Re: latest bt848 code 
In-reply-to: Your message of "Mon, 17 Mar 1997 10:54:56 EST."
             <199703171554.KAA06038@whizzo.transsys.com> 
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Date: Mon, 17 Mar 1997 10:54:57 -0700
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Hi,

> I'll do this tonight when I get home from work, and see what happens.  The
> tough part, of course, is that this comes out on the console where it might
> never be seen.  When the system hangs, the only way to recover is the 
> reset button..

you could setup the system console to be a serial port, and hook this port
to another machine.  Then you can capture a complete record of what happens.

you could hook up a switch to the NMI pin and ground.  if the kernel is wedged
behind an INTerrupt lock, this will cause a panic/core dump:

from a mailing in the archive:
----------------------------------- cut -----------------------------------
>J Wunsch <j@uriah.heep.sax.de> writes:
>   Brian, if you got physical access to the box, try placing a simple
>   card into the PC that hooks ISA pins A1/B1 to a pushbutton.  Pushing
>   it will cause an NMI (``IO channel check condition''), hopefully
>   leaving you a coredump.
>
>Anyone with a good source of ready-made cards?

I hate to suggest this, since it is both risky and a dangerous hack,
but if you can get the case off, and have a paper clip, an NMI is just
a moment away.  Bend the paper clip into a wedge shape at the end, then
short the two ISA "pins" closest to the rear end of the PC.

Don't try this at home, then blame me if it fries your motherboard!  I
have done it many a time myself, but I certainly can't guarantee it.  It's
those pesky endless loops after "cli".

Paper clip drawing (don't laugh!):

--------------------\
                     \
                     /
                ----/

Except, make it more pointy, so that it fits into the card slot, and
makes good connection.


Slot:

+-------------+ +------------------------------------a+
|             | |                                     |
+-------------+ +------------------------------------b+

Short the last two pins a and b ---------------------^
----------------------------------- cut -----------------------------------

I DEFINATELY suggest the switch method, have it set up ready to go, then
run your experiment.  push the button when the system wedges and you hopefully
will get a panic.  DON'T try this unless you understand the process and
are comfortable with it.  That unused turbo switch might be just the
thing for the job.

--
Steve Passe	| powered by 
smp@csn.net	|            Symmetric MultiProcessor FreeBSD