Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!gatech!ncar!tank!nic.MR.NET!hal!ncoast!allbery
From: allbery@ncoast.UUCP (Brandon S. Allbery)
Newsgroups: comp.os.minix
Subject: Re: BIOS disk driver
Message-ID: <13219@ncoast.UUCP>
Date: 7 Dec 88 23:04:57 GMT
References: <79151@sun.uucp> <1730@ast.cs.vu.nl>
Reply-To: allbery@ncoast.UUCP (Brandon S. Allbery)
Followup-To: comp.os.minix
Organization: Cleveland Public Access UN*X, Cleveland, Oh
Lines: 40

As quoted from <1730@ast.cs.vu.nl> by ast@cs.vu.nl (Andy Tanenbaum):
+---------------
| In article <79151@sun.uucp> alanf%smile@Sun.COM (Alan Fargusson) writes:
| >There is a problem with calling the ROM BIOS when you are using interrupts on
| >the Z-248.  The problem is that the BIOS switches to an internal stack which
| >is very small.  If an interrupt occurs during the call to the BIOS it is
| >likely that this stack will overflow.  There are other potential problems as
| >well.
| 
| Progress at last.  Do you have any suggestions about how to fix it?  I had
| hopes that the BIOS routine would work on all machines.  Perhaps this is a
| pipe dream.  However, it seems strange that bios_wini.c does work on my
| machine, which is also a Z-248.  What is going on here?
+---------------

(1) Perhaps the PS/2 has an even smaller internal stack?

(2) I've heard that Model 50's have unusual *serial port* incompatibilities.
    If one of these involves sending an interrupt where it's not expected
    (e.g. to the floppy driver?) things could conceivably blow up.  (It
    looks suspiciously like it uses an interrupt normally used by some
    networks, since initializing the serial port on a PS/2 with Novell
    Advanced Netware installed wedges the system pretty thoroughly.  Might
    Minix be using one of those vectors for something?)

(3) Even if (2) isn't the cause, it speaks of possible *other* interrupt
    incompatibilities.  Maybe the BIOS doesn't like to be interrupted, for
    instance.  (One assumes that the BIOS clock interrupt would have some way
    of dealing with this.)  Or the BIOS hooks an interrupt vector for some
    reason *after* Minix hooks it, causing some normal interrupt to send
    the computer off executing something that won't work because DOS isn't
    loaded.

++Brandon
-- 
Brandon S. Allbery, comp.sources.misc moderator and one admin of ncoast PA UN*X
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