Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!sco!paulz
From: paulz@sco.COM (W. Paul Zola)
Newsgroups: comp.unix.xenix.sco
Subject: Re: Bootable floppy
Summary: mkdev fd failure due to "16-bit VGA" problem
Message-ID: <12176@scorn.sco.COM>
Date: 26 Nov 90 02:28:26 GMT
References: <1990Nov18.223343.564@cjbsys.bdb.com>
Sender: news@sco.COM
Reply-To: paulz (W. Paul Zola)
Organization: The Santa Cruz Operation, Inc.
Lines: 39
Followup-To:


In article <1990Nov18.223343.564@cjbsys.bdb.com> 
		cliffb@cjbsys.bdb.com (cliff bedore) writes:

    [detailed problems with creating an emergency boot floppy deleted]

I know that the original poster asked for e-mailed responses, but I think
that this is of general interest.  These symptoms are due to a hardware
problem with certain brands of 16-bit VGA cards.  

Here is an entry from SCO's Information Tools database, describing the
problem and its solution.

. Mkdev fd does not work properly with some video adapters.
. 
. KEYWORDS: mkdev fd video adapters 16 bit floppy disk filesystem root boot
. xenix unix vga 
. 
. RELEASE: SCO XENIX System V Operating System Generic
.          SCO UNIX System V/386 Operating System Generic
. 
. PROBLEM: Both 16 bit video adapters and the floppy drives use DMA channel
.          2. Therefore, when writing to, or reading from, a floppy disk drive
.          the video adapter controller may add or intercept characters from
.          the floppy disk data stream, thereby corrupting the floppy.
. 
. SOLUTION: Move the video adapter to an 8 bit slot.
. 

Note that this is a *hardware* problem, and cannot be worked around by any
software fix.  

	-p

-
Paul Zola			Software Support Engineer 
				paulz@sco.COM 
We only know in theory what we are doing.   - Kate Bush
    DISCLAIMER: I speak for myself, and not for SCO.