Thanks guys for the pointers. I still getting my head round it but will get there in the end I hope!
Dances with Unix: Yes I understand that the GPU has its own memory (frame buffer) but for some reason I thought it had to be 'mirrored' in main (system) RAM whilst in use and I think that this was the bit (from link provided by kalniel) that I was thinking of:
Existing games and other graphics applications frequently allocate virtual memory for a copy of the video memory resources that the application uses. The application uses this copy to restore the display quickly if the contents of video memory are lost. For example, the application uses this copy if the user presses ALT+TAB or if the user puts the computer in standby. Typically, the DirectX run time manages the copy on behalf of the application when the application creates a managed resource. However, an application can also manage the copy itself. The virtual memory that the copy uses is directly proportional to the video memory resources that the application allocates.
A modern graphics processing unit (GPU) can have 512 MB or more of video memory. Applications that try to take advantage of such large amounts of video memory can use a large proportion of their virtual address space for an in-memory copy of their video resources. On 32-bit systems, such applications may consume all the available virtual address space.
But the article states first:
How much virtual address space is available is not related to how much physical memory there is on the computer.
So as you all say, should be OK with 64 bit Vista. Err, right?
