From:	Ludvig Larsson <ludvig AT club-internet DOT fr>
Newsgroups:	comp.os.msdos.djgpp
Subject:	superslow simpel rep stosl, why?
Date:	Mon, 19 Oct 1998 00:26:06 +0200
Organization:	Faas-Goldhart
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To:	djgpp AT delorie DOT com
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Reply-To:	djgpp AT delorie DOT com

Just a question.

My clear-buffer routine is so slow.

I want to fill about 600.000 bytes in onepart of the memory
with a constant(not screen).
On my AmdK6-2 300mhz it takes 0.006 sec. which gives about
100millions of bytes/sec. Quite a bit right!
But should it take 3 clockcykles to clear each byte?
I'm clearing quadwords...

I'm using asm(rep stosl).

Is this normal? Is it a sort of cache thing?(my amd has 64kb on-chip,
512 kb burst and the rest is 100mhz memory).

Are my calculations wrong(actually, I just want to clear a double-buffer
for 640x480x16bit graphic mode(and a z-buffer, same size:)).

Only clearing the double-buffer and the z-buffer(no drawings at all)
slows everything down to about 80fps:(

Anybody got an idea?

Ludvig

ps: the rep-stosl is inlined asm but anyway I use -O2.

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