Mail Archives: djgpp/1998/03/24/17:18:26
On Tue, 24 Mar 1998, Shawn Hargreaves wrote:
> Does anyone here have any experience of using these VDS functions?
Sorry, I don't have any first-hand experience with VDS.
> > Why do you think conventional memory won't work on Windows?
>
> My understanding is that Windows may remap the conventional memory
> to any part of your physical RAM: otherwise how could it run
> multiple DOS boxes at the same time? It works to program the DMA
> controller directly with a conventional memory address, because
> Windows will recognise what you are trying to do and arrange for
> the memory to be remapped in a suitable way, but it has no way of
> knowing what is going on with the VBE/AF driver and graphics
> controller.
But it might be that Windows does the same kind of magic with any VDS
call as well, or for VBE/AF drivers, for that matter.
> but I'm pretty sure
> that in Windows there is no 1 <-> 1 mapping between conventional
> and physical memory...
This is correct. However, Windows does a lot behind the scenes to create
the illusion that the mapping is 1:1. Too many DOS programs assume that
and would break otherwise. I don't really know if VDS and VBE/AF are
part of this magic, but there surely is no reason to believe they aren't.
- Raw text -