From:	Thomas Demmer <demmer AT LSTM DOT Ruhr-UNI-Bochum DOT De>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Physical Memory Addresses
Date:	Wed, 18 Sep 1996 14:32:31 +0100
Organization:	Lehrstuhl fuer Stroemungsmechanik
Lines:	38
Message-ID:	<323FF9EF.59E2@LSTM.Ruhr-UNI-Bochum.De>
References:	<9609180832 DOT AA26846 AT leopard DOT proteon DOT com>
NNTP-Posting-Host:	bvb.lstm.ruhr-uni-bochum.de
Mime-Version:	1.0
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Neil Jarvis wrote:
[...lots of interesting stuff deleted...]
 
> * Requirement to allocate large amounts of memory for the DMA
> 
> Things get a lot trickier when you need a lot of memory. But here is a
> solution. The virtToPhys() routine shown below can be used to
> calculate the physical address of any malloced address.
> 
> NOTE: You must run your program with protecton level 0, i.e. use
>       CWSDPR0.EXE or PMODETSR.EXE as your DPMI servers. This disables
>       virtual memory, and prevents malloced data from being swapped to
>       disk.
> 
[...]

Alaric Williams (I think) wrote an extension for djgpp to lock
memory without using a ring 0 server. So you can have virtual memory
and a physical memory address for your buffers. The buffer will not be
below 640kB, thus will not eat up precious DOS memory.



-- 
Ciao
Tom

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* Thomas Demmer                                             *
* Lehrstuhl fuer Stroemungsmechanik                         *
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