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Mail Archives: djgpp-workers/1997/09/01/05:54:44

Sender: vheyndri AT rug DOT ac DOT be
Message-Id: <340A90A4.5BA0@rug.ac.be>
Date: Mon, 01 Sep 1997 11:53:40 +0200
From: Vik Heyndrickx <Vik DOT Heyndrickx AT rug DOT ac DOT be>
Mime-Version: 1.0
To: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
Cc: djgpp workers <djgpp-workers AT delorie DOT com>
Subject: Re: _dos_ds segment limit
References: <Pine DOT SUN DOT 3 DOT 91 DOT 970831191315 DOT 17131C-100000 AT is>

Eli Zaretskii wrote:
> 
> On Fri, 29 Aug 1997, Vik Heyndrickx wrote:

> Does a program that calls `stat', or `fstat', or `getmntent'
> considered ``normal''?  If so, they all access internal DOS data
> structures which are outside the above-mentioned areas.  They could be
> also either below or above the 640K mark, depending on how did the
> host machine load DOS.

Yes, DJ already pointed out to me that we can't really live without
_dos_ds. Beside the things I called, also structures offered by TSR and
the BIOS should be accessible, and since those usually don't reside in
fixed places we need one general DOS selector.
 
> No matter how many safe functions would you ad to the library, people
> will always want The Fastest Way Ever.  I don't see anything wrong in
> using farptr functions for accessing any address in the first MB.

I won't take people's toys, but offering a safe alternative. E.g.
limiting access to the TB through a selector could prevent a lot harm.

> What happened to the video RAM access speed survey you were
> conducting, btw?  I don't think I saw the results.  Did I miss
> something?

Well, no, I didn't publish the results as such. Because I didn't get any
report from someone who had a 32-bit video access problem and I bought
in the meantime a new computer I "forgot" all about it.

Results:
- on very slow computers (386SX) or video hardware (slow VGA, old
Hercules, ...), 32 bit goes as fast as 16 bit!
- on fast computers and video hardware, results vary, from factor 1 to
factor 2 speed up.
Since text mode output doesn't really put high requirements on
performance, it wouldn't be any problem at all to change it from 32 to
16 bits.

- Fasted systems are more than 100 times quicker than slowest!

Ofcourse all based on reports I got.

-- 
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| Vik Heyndrickx |
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- Raw text -


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