From:	Shawn Hargreaves <Shawn AT talula DOT demon DOT co DOT uk>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: reliable timer choices
Date:	Sat, 10 May 1997 22:59:31 +0100
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Distribution:	world
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	<E9xAuB DOT Jrr DOT C DOT amo AT bath DOT ac DOT uk>
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To:	djgpp AT delorie DOT com
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D J Hampson writes:
>Is everyone sure that Win95 doesn't like Allegro's timers? 

Win95 doesn't mind them any more, because I fixed the code to work
around the things that upset it in Allegro 2.1, but they aren't as
accurate when used under Win95. In DOS, the clock is programmed right
down to the hardware resolution (1/1193181 of a second, although in
practice not quite that accurate due to interrupt latency), but in Win95
it is only accurate to the nearest 1/200 of a second (5 msec). 

>I tried the triple-buffering example program (with the triangles) under 
>Win95. It gives a warning at the start ('Windows detected, this program 
>probably won't run but press a key to run it anyway' or something) but 
>I couldn't see any difference between running it under Win95 and 
>anything else (DOS, 3.1).

It is running ok, but it isn't properly synchronised with the retrace.
Look at the background as the palette fades up and down: under Win95 it
will shimmer slightly as the fade goes in and out of phase with the
retrace, while in DOS it is rock steady. Also, every now and then if you
are unlucky the page flip will get out of sync with the retrace, and
then the whole screen flickers horribly.


--
Shawn Hargreaves - shawn AT talula DOT demon DOT co DOT uk - http://www.talula.demon.co.uk/
Beauty is a French phonetic corruption of a short cloth neck ornament.

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