Date: Sun, 25 Jun 95 16:08:04 MDT From: terry@cs.weber.edu (Terry Lambert) To: wpaul@skynet.ctr.columbia.edu (A boy and his worm gear) Cc: rgrimes@gndrsh.aac.dev.com, hackers@freebsd.org Subject: Re: 2.05R reboot hangs Message-ID: <9506252208.AA12050@cs.weber.edu> In-Reply-To: <199506251912.PAA07494@skynet.ctr.columbia.edu> from "A boy and his worm gear" at Jun 25, 95 03:12:54 pm
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> I have a thought. I may be barking up the wrong tree here, and for all I
> know this could be impossible, but I suppose it wouldn't hurt to ask.
>
> I seem to recall reading somewhere that there's a BIOS routine that
> can be used for rebooting the system. Now, I know using BIOS calls is a
> no-no without a VM86 interface of some kind, but what I'm wondering
> is if it's possible to force the system back into real mode just long
> enough to call the BIOS reboot routine.
This is the keyboard reset line. That's the "BIOS" call. It's the
standard way rests are done (it's how DOS fdisk did it).
> I've been reluctant to suggest this since I don't know a) how easy it
> would be to do a 'quick and dirty' switch back to real mode, b) if it's
> even _possible_ to switch back to real mode this late in the game,
> c) whether or not the BIOS reset call exists or if it's just a figment
> of my imagination or d) if it does exist, does it reset the system
> correctly (i.e. will it cause all hardware to be reset properly).
>
> My reasoning is that the BIOS reset function should be reasonably reliable
> ("It works in DOS" and all that crap). And since we're about to kill the
> system anyway, maybe it wouldn't be that hard to jam the system back into
> real mode for the purpose of this one call (we don't necessarily have
> to be that neat about it since we don't ever intend to return).
>
> So, am I nuts, or am I nuts?
You're partly nuts.
The problem with the keyboard reset code is (apparently) that the
gate A20 has not been reenabled.
Terry Lambert
terry@cs.weber.edu
---
Any opinions in this posting are my own and not those of my present
or previous employers.
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