> As I sit here with my very expensive "IBM PC-compatible", I'm
> wondering... Is it even still *possible* to map the graphics card's
> framebuffer into the CPU's address space? Or do you have to do something
> more elaborate? Do you "talk to" the graphics card directly, or you to
> talk to the PCI-Express chipset and explicitly ask it to deliver your
> message packets? Clearly the data all passes through the PCIe chipset;
> what I'm asking is whether that's transparent to the CPU or not.

You can see the address ranges if you go to the properties of your 
graphics card in device manager (under the "Resources" tab). I suspect 
the small IO address ranges are for sending commands to the GPU (which 
you can just use CPU store instructions to access), and the larger ones 
are a map of the RAM on the card (which you use DMA for).

Typically though I don't think you will find much documentation on *how* 
to communicate with a modern desktop GPU. You might find this 
interesting though, whilst not the same architecture as a PC it does 
give a bit of an insight on a modern GPU architecture (it's the one on 
the raspberry PI):

http://www.broadcom.com/docs/support/videocore/VideoCoreIV-AG100-R.pdf

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