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Mail Archives: djgpp/2000/06/11/15:00:44.2

From: "Alexei A. Frounze" <see_below AT the_messasge_body DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: far pointers
Date: Sun, 11 Jun 2000 15:32:36 +0400
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Eli Zaretskii wrote:
> 
> The point is that it is IMHO misleading to say that V86 *allows* DOS and
> PM programs to coexist.  V86 has nothing to do with PM programs that use
> DOS.  It makes the mode switch faster in some cases, but that about all
> it does for PM programs.

Okay, if you like to change CPU mode completely and waste time, you're
welcome. If you wanna miss advantages of PMode you're welcome too. But
infact, V86 is the better way to have both PMode stuff and real-mode
programs. You may dislike coexistance here, but more or less it is present
here.

>    [V86] means programs like DOS can coexist with protected-mode programs.
> 
> My comment was that this is misleading, because V86 does nothing to
> *allow* coexistence between DOS and PM programs.  They can coexist with
> or without V86, 

But not always. :) Switching back to real mode implies that 1st MB must be
free for that. I doubt it's nice to move all the PM stuff around the RAM
just in order to run some BIOS or DOS function.

> and special measures are required in both cases to make
> that coexistence possible.
> 
> > It would be impossible to have (let's say) a disk I/O in DJGPP under
> > DOS without V86.
> 
> Please explain why do you say so.  DJGPP can work on bare-bones DOS
> machine without any V86 monitor.  All you need is CWSDPMI, and CWSDPMI is
> *not* a V86 monitor, on a vanilla DOS system it really switches the CPU to
> plain real mode (not to V86) when it calls DOS.

Well, looking through CWSDPMI sources I realize it really has nothing about
V86 under true DOS. Interesting fact...

bye.
Alexei A. Frounze
-----------------------------------------
E-mail:   alexfru [AT] chat [DOT] ru
Homepage: http://alexfru.chat.ru
Mirror:   http://members.xoom.com/alexfru


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