Date: Thu, 19 Sep 96 10:59:14 BST
Message-Id: <9609190959.AA17348@leopard.proteon.com>
From: Neil Jarvis <Neil DOT Jarvis AT proteon DOT com>
To: djgpp AT delorie DOT com
In-Reply-To: <323FF9EF.59E2@LSTM.Ruhr-UNI-Bochum.De> (message from Thomas
	Demmer on Wed, 18 Sep 1996 14:32:31 +0100)
Subject: Re: Physical Memory Addresses
Reply-To: Neil DOT Jarvis AT proteon DOT com
Mime-Version: 1.0 (generated by tm-edit 7.43)
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>>>>> "Thomas" == Thomas Demmer <demmer AT LSTM DOT Ruhr-UNI-Bochum DOT De> writes:

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

Unfortunately my second method of virtual to physical address
translation also relies on the ability to get the value of the CR3
register. (It contains the physical address of the page directory
table, used (surprisingly enough) to translate linear to physical
addresses). CR3 can only be read when running at ring 0, or in real
mode.

-- Neil Jarvis, Proteon International R&D, York, UK. (Neil DOT Jarvis AT proteon DOT com)