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Date:      Wed, 10 May 2000 22:47:17 -0400
From:      Sergey Babkin <babkin@bellatlantic.net>
To:        Peter Jeremy <peter.jeremy@alcatel.com.au>
Cc:        wc.bulte@chello.nl, hackers@FreeBSD.ORG
Subject:   Re: Can NMI drop a hanging FreeBSD kernel into DDB?
Message-ID:  <391A1F35.23F38D4A@bellatlantic.net>
References:  <00May11.070143est.115219@border.alcanet.com.au> <20000510231004.A1871@jedi.wbnet> <00May11.085127est.115442@border.alcanet.com.au>

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Peter Jeremy wrote:
> 
> On 2000-May-11 07:10:27 +1000, Wilko Bulte <wkb@chello.nl> wrote:
> >And if you force the IOCHK* line on an AT slot to GND? Would that work
> >on modern PCI machines?
> 
> Grounding IOCHK* does cause an NMI on the only PCI machine I've tried
> it on.  It looks like this is maskable in the Intel PIIX3 (and
> presumably later) chips, so it may depend on the BIOS.

Seems like most of the modern machines just don't have that
pin on the PCI bus connected anywhere. But on most of them
(though not all) the pin on ISA works. Some high-end machines
like Unisys or Compaq have an NMI button on the box (sometimes
under the cover).
 
> I don't know whether this will still work if the PCI bus is hung.  I

Most probably it won't. The keyboard is connected on most machines
below PCI, so if PCI hangs you won't be able to do anything anyway.
The same problem would be in the other direction, for PCI video
card.

-SB


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