From: Ludvig Larsson <ludvig AT club-internet DOT fr>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: superslow simpel rep stosl, why?
Date: Mon, 19 Oct 1998 20:17:49 +0200
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Eli Zaretskii wrote:
> 
> On Mon, 19 Oct 1998, Ludvig Larsson wrote:
> 
> > 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?
> 
> Why not?  On a 486 STOSD is documented to require 5 clocks per move,
> so it doesn't strike me as terribly wrong to get 3 clocks on K6.  Keep
> in mind that it doesn't just move the dword, it also increments a
> pointer and decrements a count as it goes.
> 
But? As I'm clearing d-words, each stosl takes 12 cycles...

I have trought of a way so I don't need to clear the z-buffer, but it
should be really nice to push the processor under the "4-times to slow"
limit.

Ludvig Larsson