Originally Posted by prankstare
jlippo, thanks for the clarification. But how do you explain the fact Xbox 360 almost never uses any anisotropic filtering in their titles and PS3 does? If Xbox clearly has "better" graphics hardware, including the super-fast EDRAM, why would developers sacrifice AF on this console? For the sake of FPS? I don't think so. For the 4xAA + HDR? Maybe? I thought this was a matter of disc storage space (dvd9 vs. blu-ray), but you said AF has nothing to do with memory, so I am more and more confused.
Performance is the only reason and no AF doesn't require any additional storage space when already using mipmaps. (Which you already use for performance, memory and quality reasons.)
Find the GPU related presentations from the Gamefest precentations and you will find following things.
Xenos has 32KB of texture cache and thus in recommended not to use trilinear with anisotropic filtering and if trilinear is used to use method which blends only very near mipmap is changed.
Simply put, when the cache is trashed the GPU stalls and you waste a lot of good rendering time.
Also all textures reside within main memory and use it's bandwidth, so textures do not use any storage or bandwidth from edram.
Daughter die doesn't have ALUs or TEX units, so the texturing or any alu related calculations cannot happen there, only write operations from ROPs. (only read operation is during for blendin transparent surfaces.)
Here's a couple of presentations which should get you started.