From:	arg AT whangomatic DOT freeserve DOT co DOT uk (Andrew R. Gillett)
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Vsync!
Date:	Thu, 29 Jul 1999 21:33:56 +0100
Organization:	www.release-dates.co.uk
Message-ID:	<MPG.120aa676627c395098af48@news.freeserve.net>
References:	<6uAn3.7443$ip4 DOT 11733 AT nntpserver DOT swip DOT net> <MPG DOT 12091975248925af98af34 AT news DOT freeserve DOT net> <vVEn3.7593$ip4 DOT 12531 AT nntpserver DOT swip DOT net> <379f2171 DOT 0 AT news DOT uni-bielefeld DOT de> <KAMn3.8254$ip4 DOT 12338 AT nntpserver DOT swip DOT net> <MPG DOT 1209ac5b865383f298af43 AT news DOT freeserve DOT net> <9bVn3.8378$ip4 DOT 12411 AT nntpserver DOT swip DOT net> <37a027bc DOT 0 AT news DOT uni-bielefeld DOT de> <ki_n3.8510$ip4 DOT 13228 AT nntpserver DOT swip DOT net> <7nptn7$6ks$1 AT taliesin DOT netcom DOT net DOT uk>
NNTP-Posting-Host:	modem-103.thinker.dialup.pol.co.uk
X-Trace:	news5.svr.pol.co.uk 933280466 28595 62.136.107.103 (29 Jul 1999 20:34:26 GMT)
NNTP-Posting-Date:	29 Jul 1999 20:34:26 GMT
X-Complaints-To:	abuse AT theplanet DOT net
X-Newsreader:	MicroPlanet Gravity v2.11
Lines:	32
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp
Reply-To:	djgpp AT delorie DOT com

In comp.os.msdos.djgpp, Michael Stewart wrote:
> Knutte wrote in message ...
> >A few minutes after I wrote this I tried to force Allegro to use VESA 1.0
> >instead of Autodetect. The Attempt was successful so the problem lies
> within
> >the communication between Allegro and my GFXcard.  Thank you all for the
> >help
> 
> 
> I'd be suprised if that was the case. Any problems with vsync would have
> been sorted out a long time ago.
> 
> This is the `standard' method of waiting for the vertical retrace (I would
> think Allegro will be similar if not the same). Try it and see if this
> works.
> 
> void vsync () {
>   while (inportb (0x3DA) & 8);
>   while (! (inportb (0x3DA) & 8));
> }

I already answered this question quite a while ago. Some video cards 
simply don't support vsync. It is the fault of the video card 
manufacturer. This was done with some video cards several years ago when 
Quake timedemos were an important benchmark. Disabling vsync in Quake 
gives a tiny frame rate improvement. Some video card manufacturers 
deliberately ommitted the vsync facility so that their card would always 
get a 0.1 second timedemo improvement in Quake. Pretty pathetic.

-- 
Andrew Gillett      http://argnet.fatal-design.com/     ICQ: See homepage
"I've always wanted to be a sandcastle." - Chelmer Monkton, Starship Losers

- Raw text -