From:	Nigel Stephens <nigel AT algor DOT co DOT uk>
Date:	Thu, 18 May 95 16:38:33 +0100
To:	Charles Sandmann <sandmann AT praline DOT no DOT NeoSoft DOT com>
Cc:	djgpp AT sun DOT soe DOT clarkson DOT edu
Subject:	Re: RM functions with DJGPP
References:	<199505172028 DOT NAA03954 AT kendaco DOT telebyte DOT com> <199505181256 DOT HAA28675 AT praline DOT no DOT NeoSoft DOT com>

Charles Sandmann (sandmann AT praline DOT no DOT neosoft DOT com) writes:
 > Joel Hunter wrote:
 > >   I realize that starting with 2.0, DJGPP-compiled programs will operate
 > > only under a DPMI environment, and as such many hardware-interrupt issues
 > > will be more easily resolved.  However, sometimes your need for speed is so
 > > great that you want NO mode-switching when the interrupt occurs.  In these
 > > cases, you need a real-mode handler for when the interrupt occurs in
 > > real-mode.  Will we be able to do this in version 2?  (Even if it has to be
 > > pure assembly I think it would still be very useful.)  
 > 
 > Here you are at the mercy of the DPMI provider you are using.  If you hook
 > both RM and PM interrupts, you should hook the PM interrupt first (since it
 > modifieds the RM interrupt to reflect).  If the PM interrupt does an IRET
 > and does not chain, then you would not need the extra mode switches, if the
 > DPMI provider allows this (I think it would work under CWSDPMI).

Can you clarify this?  Under GO32 v1.x I believe that it was necessary
to install both a protected-mode handler AND a real-mode handler, to
ensure that interrupts weren't missed when GO32 switched to real-mode
to call DOS/BIOS.

Is it true that a program using GO32 v2 (or any other "real" DPMI
provider) runs totally in protected mode, using V86 mode to access
DOS/BIOS functions, and that a real-mode handler is no longer
absolutely required.

Regards

Nigel

-- 
 _________________________________________________________________________
 Nigel Stephens, Algorithmics Ltd, 3 Drayton Park, London, N5 1NU, England
 mailto:nigel AT algor DOT co DOT uk			    http://www.algor.co.uk
 phone:+44 171 700 3301				      fax:+44 171 700 3400

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