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Date:      13 May 1998 09:43:23 +0200
From:      dag-erli@ifi.uio.no (Dag-Erling Coidan =?iso-8859-1?Q?Sm=F8rgrav?= )
To:        jjw@us.net
Cc:        "=?iso-8859-1?Q?=22Dag?= -Erling Coidan =?iso-8859-1?Q?Sm=F8rgrav=22?=  <dag-erli@ifi.uio.no>=?iso-8859-1?Q?=2C?=  Andrew Short" <dag-erli@ifi.uio.no>, stable@FreeBSD.ORG
Subject:   Re: PC Keyboard Ctrlr Chip (was: PPP hard lock in 2.2.6)
Message-ID:  <xzp3eeesjj8.fsf@hindarfjell.ifi.uio.no>
In-Reply-To: John Woodruff's message of "Tue, 12 May 1998 18:34:26 -0400"
References:  <Pine.SUN.3.96.980512135132.23087D-100000@galileo.cris.com> <xzplns76zlv.fsf@hrotti.ifi.uio.no> <3558CE72.2300BB70@us.net>

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John Woodruff <jjw@us.net> writes:

> Andrew Short <Ashort@concentric.net> writes:
> > 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.
> 
> Dag-Erling Coidan Smørgrav wrote:
> > [...] 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 [...]
> >
> > 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).
> 
> The 8042 is a general-purpose single-chip computer/controller; which
> has been used since the dawn of time (or at least of the IBM PC/AT)

Yup, the original PC and XT used the 8048. I know all that... what I
was looking for was programming information - I know that outputting
0xfe to port 0x64 makes the 8042 assert the reset pin on the CPU, but
I want to know *why* :)

> Seems odd, but AFAIK the standard program has no way of triggering
> the CPU reset on command from the keyboard - the main CPU has to
> *ask* to be reset, which is why Ctrl-Alt-Del does nothing to a
> hard-locked (or -looping) CPU.

It shouldn't really be a problem to design a keyboard with this
possibility.

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