Message-ID: <38B7B9D8.EEF32B26@bigfoot.com>
From: JP Morris <doug-15 AT bigfoot DOT com>
Organization: Aircraft Liberation Front
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Newsgroups: comp.os.msdos.djgpp
Subject: Re: Fastest bitblt?
References: <38B73FC4 DOT 82FCECB8 AT videotron DOT ca>
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Date: Sat, 26 Feb 2000 11:32:40 +0000
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

Trancelucid wrote:
> 
> Hi there,
>         I'm porting some source of mine (from Watcom and TC) to DJGPP, and the
> main problem I'm having right now is accessing 0xA0000. I read the libc
> reference, and a few tutorials on the net, and the most popular
> buffer-to-video functions seem to be memcpy() and _farpokeb().. I have
> some unanswered questions, and I'd like your opinion on the matter.
> 
> It may be off-topic, but just for curiosity... Why can you access
> 0xA0000 in Watcom and not in DJGPP? Both are 32bit compilers, so why
> would you need to disable protection to access video memory in DJGPP?
> 
> How (un)safe is it to disable protection to access video memory with
> memcpy()?
> 
> As for _farpokeb(), is there a way to make it faster? Right now I use it
> in a for loop:
> 
> for(i=0;i<64000;i++)
>    _farpokeb(_dos_ds,0xA0000,+i,buffer[i]);
> 
> Also, when I use optimization parameters (-O3), both seem the same
> speed.. Are they the same code when optimized? And how can I look if
> they use the same asm instructions?
> 
> Is there any faster way than those 2?

How about writing a little assembly to do the blit using rep movsd?
Then you can set ES to the video segment and away you go.

> 
> TIA,
>         .(Trancelucid).
>           .  Jaune  .

-- 
JP Morris - aka DOUG the Eagle (Dragon) -=UDIC=-  DOUG-15 AT bigfoot DOT com
Fun things to do with the Ultima games            (http://ithe.cjb.net)
Developing a U6/U7 clone                          (http://fly.to/ire)
d+++ e+ N+ T++ Om U1234!56!7'!8!KA u++ uC+++ uF+++ uG---- uLB----
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