From: peet@locus.com (J. David Peet)
Subject: Re: Dell issue 2.2 video
Organization: Locus Computing Corp, Los Angeles
Date: Fri, 06 Nov 1992 03:56:06 GMT

In article <1992Nov5.071707.17297@thunder.mcrcim.mcgill.edu> bruno@athena.mcrcim.mcgill.edu (Bruno Hall) writes:
>
>I just got myself an ATI Graphics Ultra, and am mostly pleased with
>it.  Under Dell 2.2, running Xmach at 1024x768x256, on a (very non-Dell :-)
>486-33, I'm getting 68,000 Xstones.  It's *great*.
>
>BUT I can't seem to make a native VGA DOS image under Merge.  The
>screen just blanks out, and the thing sits there.  What this means is
>that I can't access any of the non-standard VGA modes under DOS.  Same
>story on another machine (different hadrware brand).
>
>Has anyone managed to do this with a Graphics Ultra?
>
>Naturally, neither Dell nor Locus answer my mail on this topic, which
>seems strange, particulary since this card is actually supported
>by Dell, and is a name-brand item to boot. 

Please, I did answer your mail!  My e-mail answer got damaged, and earlier
today I got e-mail from you in which you stated that you had received
a screwed up e-mail answer from me.  I was fully intending to try again
tonight after I finished my regular tasks.  Please give us a little time to
reply before flaming.  (What if I was on vacation or sick, or was somehow
prevented from using e-mail?  A few weeks ago our e-mail and net-news
connection machine completely died (probably taking a few messages down with
it), and took a day or so to replace it and get e-mail working again, and
more than a few days to get news flowing again.)

My reply is this:  Making "native" VGA DOS images only works for a few
VGA cards.  This is a known restriction.  In the future, it is intended
that more cards will be made to work, most likely involving special
code for each new card.

Making "native" (a.k.a. on-card-ROM) images is an inherently dangerous
thing to do (e.g. it can lock up the machine), but if it the image file
get made, then it is safe to use.  Making "standard" VGA images is
inherently SAFE, so that is the default one that is made and used.

The reason it is dangerous is not due to a "bug", but due to the fact that
for the boot code in most VGA ROMs to work, we must give it more control
over the real machine than is normally done.  Thus if the boot time code
has problems because it is trying to do something that just cannot be
supported with the current version of Merge, it can hang the machine.
In several cases I know, VGA ROM boot code plays with the system timer,
which also controls the RAM refresh.  Having the RAM refresh turned off
is a very fast way to hang your machine.

--------------------------------------------------------------------- 
David Peet     Internet: peet@locus.com   UUCP:...!uunet!lcc!peet  
Locus Computing Corporation, 9800 La Cienega Blvd. Inglewood, CA 90301
               Fax:(310)670-2980  Voice:(310)670-6500
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Disclaimer: Normally my statements are my own, and not do not
necessarily reflect those of Locus, but maybe this time they do,
but then again, maybe not.
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Newsgroups: comp.unix.sys5.r4