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Date:      12 May 1998 21:47:08 +0200
From:      dag-erli@ifi.uio.no (Dag-Erling Coidan =?iso-8859-1?Q?Sm=F8rgrav?= )
To:        Andrew Short <Ashort@concentric.net>
Cc:        stable@FreeBSD.ORG
Subject:   Re: PPP hard lock in 2.2.6
Message-ID:  <xzplns76zlv.fsf@hrotti.ifi.uio.no>
In-Reply-To: Andrew Short's message of "Tue, 12 May 1998 14:00:37 -0400 (EDT)"
References:  <Pine.SUN.3.96.980512135132.23087D-100000@galileo.cris.com>

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Andrew Short <Ashort@concentric.net> writes:
> On Tue, 12 May 1998, Forrest W. Christian wrote:
> > On Tue, 12 May 1998, Brian Somers wrote:
> > > It's not a problem I've seen.  It's *very* unlikely that ppp is 
> > > wedging the whole machine :-/  but possible I guess...
> My (I use it at work, I am not lucky enough to OWN one!) Sun UltraSparc
> has a feature that will arrest control from the OS by doing a Stop-A on
> the keyboard.

Now, I'm not an expert on Sun internals, but UiO is mainly a Sun shop
so: what this does is generate a (nonmaskable) interrupt which drops
the machine into the BIOS prompt. This is entirely hardware-driven and
AFAIK non-intrusive (i.e. if you press Stop-A by accident, just type
'c' to resume operation) except that it f*s up your display. There is
no way to do this on a PC, unless some bright motherboard vendor somes
up with the idea of producing a motherboard that e.g. drops to a BIOS
prompt when the keyboard controller (i8042) asserts the reset pin
(which is how FreeBSD reboots when you fastboot or shutdown -r) and
somebody builds a keyboard with a key (or preferably a switch hidden
underneath the keyboard) which triggers this event.

I tried to find information about the 8042 on Intel's web site, but
there doesn't seem to be any (except for references to it in chipset
or motherboard datasheets).

> I have a gut feeling that "stop-a" is somehow embedded in the Sparc
> hardware...but I have to ask.

It is.

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