X-Authentication-Warning: delorie.com: mail set sender to djgpp-bounces using -f
X-Recipient: djgpp AT delorie DOT com
From: "Gerrit van Niekerk" <gerritvn AT gpvno DOT co DOT za>
Organization: GPvNO
To: djgpp AT delorie DOT com
Date: Mon, 24 Sep 2007 17:39:49 +0200
MIME-Version: 1.0
Subject: DMA and paging
CC: gerritvn AT gpvno DOT co DOT za
Message-ID: <46F7F665.1773.20651AE9@gerritvn.gpvno.co.za>
X-mailer: Pegasus Mail for Windows (4.41)
Content-type: text/plain; charset=US-ASCII
Content-transfer-encoding: 7BIT
Content-description: Mail message body
Reply-To: djgpp AT delorie DOT com

The DJGPP FAQ (http://www.delorie.com/djgpp/v2faq/faq18_13.html) tells 
me to use XMS when a large DMA buffer is required, do some mapping 
tricks and use farptr functions to transfer between DJGPP memory and the 
DMA memory. My understanding is that paging is to blame for this 
complexity. 

My question: If paging is disabled by either configuring CWSDPMI with 
CWSPARAM or using CWSDPR0, will the physical to logical address 
mapping be 1:1? Can the physical address to program the DMA unit be 
simply computed by the data segment and offset?