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From:	Charles Sandmann <sandmann AT clio DOT rice DOT edu>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: physical adress of int
Date:	Sat, 11 Sep 2004 13:53:15 CDT
Organization:	Rice University, Houston, TX
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> I want to know a physical adress of my int variable, it's for my ethernet
> board for his initialisation.

In general under DPMI you can't do this.  However, it depends a lot on your
environment.  Frequently the 640KB area is mapped 1:1 - so you can put
data there suitable for DMA usage.  Since Windows can virtualize the DMA ports,
it will even remap requests to the first 640KB, so this technique works 
well in many environments.

If you need larger memory buffers that will not fit in the DOS memory area,
and are willing to stick to a single DPMI provider, you can use PMODE without
VCPI (which doesn't enable paging) so your virtual address is the same as
the physical address (you need to add the DS base to it's address).

If you need a more compatible DPMI, you can use CWSDPMI and the files from
http://clio.rice.edu/djgpp/cwsdma2.zip

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