From:	"Peter Remmers" <pitti AT tfh-berlin DOT de>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Using Vitual DMA Services...help !
Date:	Mon, 1 Feb 1999 19:54:14 +0100
Organization:	TFH-Berlin (Berlin, Germany)
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James Deuchar schrieb in Nachricht
<01be4dfb$0d10fde0$f2cfea81 AT secom144 DOT dur DOT ac DOT uk>...
>Help.....! I'm still trying to get my DMA to work so I need to get the
>actual phy mem address. The VDS method is preferable to copying data into a
>buffer below the 1M mark and dmaing that because speed is a factor. What's
>wrong with my code (or right with it)........I always get some sort of
>error code back...often in reserved registers...please help!


I had the same problem. I couldn't get VDS to return the physical address of
a malloc'd buffer (not coninuous or so), allocating one with VDS didn't work
either,
I needed a buffer of about 2MB which was too big for VDS.
Then the problem was that it worked under plain DOS but not in a W95 DOS
box.

Then someone told me I should use XMS, which solved my problems.
Allocate your buffer with XMS use the XMS lock handle function to get the
physical
address. Then you can either build a selector for that physical address or
use
the XMS moving functions to access that buffer.

> //check for VDS at bit 5 of mem 0x0040:007b  ----   HOW CAN I CHECK THIS
>BIT????


That would be something like
  _farpeekb(__dos_ds, 0x4007) & 0x20

good luck!

Peter Remmers

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