Q: to video addressing system

Hello. In a talk-back thread regarding some graphics cards tests some anonymous guy posted the following and corrected me.
Since he's anonymous I can't mail him and ask him more. But is he right? I would find it odd for the OS to present video memory space as system storage space for a game or other 3d accellerated application. I'd assume those new of the presense of the video memory directly, and would address that instead of system memory.

The source of the debate was, that someone claimed the amount of graphics card memory would impact the available memory in a 32bit system equipped with 4gb. ie. a card with 768mb memory might eat up more of the 3,2-4gb range than one with 256mb .... which in my world sounds silly. I was told, by otherwise literate people, that the amount of available memory is the result of various bios settings.

"When the OS loads the actual graphics drivers, it assigns a region of the address space to the graphics card. If there is enough unused address space, it gives it that, else it will overlap some of it with system RAM. This RAM is then mapped into an application's address space when taking advantage of hardware acceleration - so it can copy textures and write graphics commands - and hidden behind OpenGL and Direct3D."
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More about video addressing system
  1. A 32 bit OS can only address 4Gb of memory in total and will `steal` from system memory allocation in order to address other components such as sound and graphics cards.
    For example; My rig, has 4Gb installed RAM under 32 bit XP and a 512Mb 4870 card and X-Fi sound. Windows reports 3.25Gb of sytem memory available because it has allocated .75Gb for the sound and video cards, 3.25+.75=4.00.
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