From:	Ludvig Larsson <ludvig AT club-internet DOT fr>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Graphic Speed and memory
Date:	Fri, 23 Oct 1998 03:35:24 +0200
Organization:	Faas-Goldhart
Lines:	34
Message-ID:	<362FDD5C.2212@club-internet.fr>
References:	<362F1A03 DOT C49DA4C1 AT phreaker DOT net> <70nq5e$11m AT newsops DOT execpc DOT com>
NNTP-Posting-Host:	toulouse-camichel9-100.club-internet.fr
Mime-Version:	1.0
X-Trace:	front1.grolier.fr 909108142 25200 195.36.147.100 (23 Oct 1998 02:02:22 GMT)
NNTP-Posting-Date:	23 Oct 1998 02:02:22 GMT
X-Mailer:	Mozilla 3.01C-CLUB (Win95; I)
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp
Reply-To:	djgpp AT delorie DOT com

Alan Bork wrote:
> 
> > First of all, I'd like to know which of those takes longer to refresh?
> >
> > 800x600x15bit
> > 640x480x32bit
> >
> > Second, how do you calculate how much memory it takes?
> 
> I am not sure about the refresh but the memory is easy enough.
> First note that the 15 bit will be treated as 16 bit and just
> throwing away the extra bit.
> 
> 16 bit is 2 bytes
> 32 bit is 4 bytes
> (we all know that so...)
> 
> 800 * 600 * 2 = 960000 bytes or 937.5 KB
> 640 * 480 * 4 = 1228800 bytes or just over 1.17 MB

I had some "strange" slowdown problems with my clear-boublebuffer
routine, and well, the boundare for clearing a this large block in
memory isn't the processor speed but the memory speed.

Ex. clearing 600.000bytes took 0,006 sec but clearing
6000 bytes 100 times(=600.000) took 0,002 sec...(because the memory was
loaded in the cache onchip and is about 3 times faster than ordinary
memory, on my machine).
so, if you have 100mhz memory, expect to be able to clear 1mb in about
0,01 sec.

hth

Ludvig Larsson

- Raw text -