From:	mvparvia AT kvartsi DOT hut DOT fi (Mikko V.I. Parviainen)
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Allegro and blitting to screen
Date:	19 Jul 98 18:34:21 GMT
Organization:	Helsinki University of Technology, CS lab
Lines:	27
Distribution:	world
Message-ID:	<mvparvia.900873261@snakemail.hut.fi>
References:	<6onnuh$12p$2 AT oravannahka DOT Helsinki DOT FI> <MPG DOT 101ad9bbc1569c84989988 AT news DOT virgin DOT net>
NNTP-Posting-Host:	kvartsi.hut.fi
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

a DOT gillett AT virgin DOT net (Andrew R. Gillett) writes:
>In comp.os.msdos.djgpp, article <6onnuh$12p$2 AT oravannahka DOT Helsinki DOT FI>, 
>Tuomo A Turunen (tuturune AT cc DOT helsinki DOT fi) wrote:
>> HELP !!??
>> I'm programming a very nice game with DJGPP and allegro. I use SVGA
>> 640*480*256 colors, so graphic looks good. But the problem is the
>> double buffering. It's just too slow.

>I've never understood the point of double-buffering. Are there any 
>advantages over page flipping?

Some time ago I made some tests in 640*480*256 mode. I have an P100
machine, with some very bad SVGA card. 
My test program used the whole screen. First, I tried page flipping.
It was annoyingly slow, so I decided to try double buffering, 
because it was very quick to code. The speed gain was unbelievable.
The blit was about two times as quick as with double buffering.
I think that the cause of this effect was the slowness of
video memory, but I am not sure. 

So, in my experience drawing to video memory can be very slow, and
double buffering a viable option sometimes.     
-- 
--
Mikko Parviainen
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