From:	Charles Sandmann <sandmann AT clio DOT rice DOT edu>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: DMA and DJGPP
Date:	Sat, 18 Jan 2003 10:59:47 CST
Organization:	Rice University, Houston TX
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> I'm building a data aquisition board that uses a PLX PCI chip to
> communicate with the PCI bus. I need to set it up to use DMA to transfer
> the data. I how to do I find the address and set up the memory in DJGPP
> to get at the data?

This all depends on the environment, and how big a DMA buffer you need.

The typical way of handling this is using a 64K to 256K buffer and placing
it in the conventional memory memory area.  This memory is mapped 1:1 in
DOS - and Windows 9x does virtualization to make it look like it's 1:1.  
I'm not sure on WinNT/2K/XP how well it virtualizes this.

If you need a big DMA buffer (>256K) it depends on the environment.  Under
pure DOS and CWSDPMI there is example code available to examine the page 
tables and get the physical addresses of the memory:
http://clio.rice.edu/djgpp/cwsdma2.zip

There are also methods described in the FAQ to handle this, check it also.

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