> Can anyone give me a run down of how a vid. cards memory is used?
> For example, a Geforece4 has 128 meg memory. How is this memory used? Is
> it shared between the framebuffer geometry and textures, is it just used
> for for texturs etc
Brad,
Good question! Here is a quick answer, and perhaps others can elaborate:
All consumer graphics cards (e.g. NVIDIA GeForce series) use "unified" memory: the onboard memory is shared between the framebuffer and texture data. This means that the higher the resolution / color-depth for your framebuffer, the less memory you have for texture data. Some professional graphics cards (e.g. 3Dlabs Wildcat) still have separate framebuffer and texture memory, presumably using two different kinds of memory.
When a graphics card runs out of texture memory (usually by allocating too much texture data) the card has to move some of the data to system memory over the AGP bus. Using system memory is much slower than using local memory: once you get into such a "swapping" state, performance will suffer. This is why you now see games specifying a minimum amount of graphics card memory, usually 32 MB.
(However, I don't know how/where display lists are stored. My understanding is that geometry is not actually stored on the graphics card unless it is in a display list.)
I hope that helps!
- Mauricio
