Message-Id: <m0z8sj2-000S3uC@inti.gov.ar>
Comments: Authenticated sender is <salvador AT natacha DOT inti DOT gov DOT ar>
From: "Salvador Eduardo Tropea (SET)" <salvador AT inti DOT gov DOT ar>
Organization: INTI
To: jpdelprat AT teaser DOT fr (JP), djgpp AT delorie DOT com
Date: Tue, 18 Aug 1998 18:01:44 +0000
MIME-Version: 1.0
Content-type: text/plain; charset=US-ASCII
Content-transfer-encoding: 7BIT
Subject: Re: How to determine the physical address from a DPMI descriptor
In-reply-to: <35d9d505.4345933@news.teaser.fr>
Precedence: bulk

jpdelprat AT teaser DOT fr (JP) wrote:
> Eli Zaretskii <eliz AT is DOT elta DOT co DOT il> wrote:
> 
> >
> >On Sun, 16 Aug 1998, JP wrote:
> >
> >> I've allocated a large array, locked it and set a descriptor to this
> >> array. I would like to know the physical address of this array. Can it
> >> be determined from the descriptor ?
> >
> >In general, you can't.  You can only find the logical address, not the 
> >physical one.
> >
> >Please explain why do you need the physical address, then it would be 
> >possible to advise about any available solutions.
> > 
> 
> My need is to create and lock a 2Mo continuous buffer (under Windows
> 95), and 
> determine its physical address to give it to a video capture card. 
> 
> Determining the physical address shouldn't be a problem since 
> there are solutions to explore the entire physical memory, but I can
> find any solution to create a continuous buffer.
> 
> 
> With DPMI functions (under Windows 95), I allocate my buffer then 
> lock it, but despite the call to dpmi_lock_linear_region, the buffer
> is still mixed and partially swapped out.
> 
> I've tried everything I could think of. I've even tried to allocate
> and lock an XMS buffer in my autoexec.bat (before Windows 95 loads),
> but Windows 95 refuses to start then.
> 

How did you tried it? I think you must use the options to reserve a portion 
of memory. HIMEM have some switches to reserve memory and don't include it in 
the XMS pool. Is that what you tried? I think this memory can be used with 
some old BIOS service (int 15?). I saw something about it in the help of 
HIMEM from DOS 6.2.
Another way could be the use of native Win API calls. Is hard to do it from 
djgpp but some functions can be called. I don't know  if you can use the 
memory allocation stuff.
A nasty one: Try reducing the amount of memory reported by BIOS and use it. 
Some mother boards lies when reporting the installed memory because the 
on-board video chip uses the DRAM as video memory, you can use a similar 
trick.

SET
------------------------------------ 0 --------------------------------
Visit my home page: http://set-soft.home.ml.org/
or
http://www.geocities.com/SiliconValley/Vista/6552/
Salvador Eduardo Tropea (SET). (Electronics Engineer)
Alternative e-mail: set-soft AT usa DOT net set AT computer DOT org
ICQ: 2951574
Address: Curapaligue 2124, Caseros, 3 de Febrero
Buenos Aires, (1678), ARGENTINA
TE: +(541) 759 0013