From owner-freebsd-emulation  Mon Sep  1 19:01:43 1997
Return-Path: <owner-freebsd-emulation>
Received: (from root@localhost)
          by hub.freebsd.org (8.8.7/8.8.7) id TAA07136
          for emulation-outgoing; Mon, 1 Sep 1997 19:01:43 -0700 (PDT)
Received: from genesis.atrad.adelaide.edu.au (genesis.atrad.adelaide.edu.au [129.127.96.120])
          by hub.freebsd.org (8.8.7/8.8.7) with ESMTP id TAA07124
          for <emulation@FreeBSD.ORG>; Mon, 1 Sep 1997 19:01:36 -0700 (PDT)
Received: from word.smith.net.au (lot.atrad.adelaide.edu.au [203.20.121.21]) by genesis.atrad.adelaide.edu.au (8.8.5/8.7.3) with ESMTP id LAA26910 for <emulation@FreeBSD.ORG>; Tue, 2 Sep 1997 11:31:32 +0930 (CST)
Received: from word.smith.net.au (localhost.atrad.adelaide.edu.au [127.0.0.1])
	by word.smith.net.au (8.8.7/8.8.5) with ESMTP id LAA00629;
	Tue, 2 Sep 1997 11:26:19 +0930 (CST)
Message-Id: <199709020156.LAA00629@word.smith.net.au>
X-Mailer: exmh version 2.0zeta 7/24/97
To: Jonathan Mini <j_mini@efn.org>
cc: Mike Smith <mike@smith.net.au>, emulation@FreeBSD.ORG
Subject: Re: Fun with DOSCMD (was Re: modifying boot mgrs FROM FREEBSD) 
In-reply-to: Your message of "Mon, 01 Sep 1997 02:42:17 MST."
             <19970901024217.20763@micron.efn.org> 
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Date: Tue, 02 Sep 1997 11:26:18 +0930
From: Mike Smith <mike@smith.net.au>
Sender: owner-freebsd-emulation@FreeBSD.ORG
X-Loop: FreeBSD.org
Precedence: bulk

> > It certainly makes no sense to attempt to reenter the video BIOS, but 
> > in at least the trivial sense there is nothing stopping me calling, 
> > say, an ESCD function in one virtual x86 context while the video BIOS 
> > is being called in another; remember that they are operating in 
> > distinct virtual contexts, where the only risk of conflict is in the
> > I/O domain.
> 
> Umm. I hope you are rembering about memory-address registers? :)

That is indeed what "I/O domain" means; the only resource shared 
between vm86 threads is hardware.

>   My problem is : "why can't I call the disk simulator's BIOS when I am using
> the video simulator's BIOS at the same time?" and there are too many reasons
> why not. (things like asking for a keypress and askingfor disk i/o
> simultaneously will crash Win95) 

I don't think I understand you here.  You are saying that someone 
else's BIOS implementation is nonreentrant, correct?  That's more or 
less to be expected...

mike