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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 |
Lines: | 16 |
Message-ID: | <4143499b.sandmann@clio.rice.edu> |
References: | <chrpjm$r73$1 AT s5 DOT feed DOT news DOT oleane DOT net> |
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NNTP-Posting-Date: | Sat, 11 Sep 2004 19:07:10 +0000 (UTC) |
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To: | djgpp AT delorie DOT com |
DJ-Gateway: | from newsgroup comp.os.msdos.djgpp |
Reply-To: | djgpp AT delorie DOT com |
> 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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