Message-ID:	<3426BC71.7420@EnchantedLearning.com>
Date:	Mon, 22 Sep 1997 11:44:01 -0700
From:	Mitchell Spector <spector AT EnchantedLearning DOT com>
Reply-To:	spector AT EnchantedLearning DOT com
Organization:	Enchanted Learning Software
MIME-Version:	1.0
To:	djgpp AT delorie DOT com
CC:	Ben N Shadwick <bshadwick AT juno DOT com>
Subject:	Re: DJGPP, interprocess communication, and DPMI
References:	<341FEC5F DOT 77F2 AT EnchantedLearning DOT com> <3420BBED DOT 23F69891 AT juno DOT com>
	<3420D008 DOT 1E80 AT enchantedlearning DOT com> <19970918 DOT 224538 DOT 13566 DOT 0 DOT bshadwick AT juno DOT com>

Ben N Shadwick wrote:
> 
> On Wed, 17 Sep 1997 23:54:00 -0700 Mitchell Spector
> <spector AT EnchantedLearning DOT com> writes:
> >Interesting...  I haven't seen this on my machine, at least not
> >flipping between a full-screen DOS box and the Win95 screen.  What
> >video mode do you find exhibits this problem?  After reading your
> 
> Well, I use 640x480x256 in Win95 because that's the fastest mode I can
> get (I have an ancient TVGA8900 ISA video card - I really want a good 2mb
> VLB one). If I run a 640x480x256 DOS program and then, say, hit the Win95
> key, Win95 will overwrite the video memory with the desktop, so that when
> I try to return to the program, it kills it (because it can't restore the
> screen because it has already destroyed what was in the video memory). At
> least that's my theory... I suppose it might be able to save a copy of
> video memory IN video memory IF you have enough, but I doubt that Win95
> is that smart... The important thing is to make sure that Win95 and the
> DOS program are both using the EXACT same SVGA mode (though I haven't
> tried it otherwise I guess)

I set up a DOS program using exactly the same SVGA mode as my
Win95 screen, used Alt-Tab to switch back and forth between the
Win95 desktop and the full-screen DOS program, and it worked
correctly on my system (except for not restoring the border colors).
Maybe Win95 tries to save the video memory of the swapped-out process
if it can find enough RAM (or virtual memory) to do it?

> >message, I tried a variety of 256-color SVGA resolutions, but couldn't
> >get Win95 to flake out in that way.  One thing it never does correctly
> >is to restore the border color in the DOS screen if you've changed
> 
> Yes I've noticed that with some 320x200 progs I have - it makes palette
> color 0 be weird colors sometimes when I flip back. It can be very
> annoying.
> 
> >it; there may well be other things that don't get saved and restored
> >either.  And I do find that flipping between two DOS boxes can cause
> >the problem you mentioned.
> 
> I guess the bottom line is just that Win95 isn't... as reliable as it
> could be, or as reliable as some people have been led to belive at least
> (not me =)

Well, I wasn't claiming any sort of robustness here :-).  But,
actually, I haven't found Win95 to be as unstable as a lot of
people say (although it's not nearly as stable as Unix, of course).

> =====
> Ben Shadwick, Sysop, Mars Base BBS, (360)882-0773, Vancouver, WA, USA

Mitchell
--
Mitchell Spector, Enchanted Learning Software
E-mail: spector AT EnchantedLearning DOT com
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