tiling is disabled by default on r3/4xx cards so it shouldn't affect you. someone needs to figure out how to properly enable it on r3/4xx cards (for both 2d and 3d). Once it is figured out it should provide a nice boost in performance.
Alex,
Could you explain to me what tiling is ? I thought it is simply a way to render images larger than 2048x2048, in which case I do not see how it can increase performance (ignoring things like cache sizes)
There is a "TILING" register in R300 which we set, but I believe it refers to something different - partioning rendering into small squares (like 16x16) for the benefit of the rendering engine.
that's pretty much what tiling is. you can represent the framebuffer either linearly, or as a series of fixed size tiles. for example, you might bave fixed size tiles of 1024 bytes. so each tile would be 16 pixels x 16 pixels x 4 bytes for depth 24 and 32x16x2 for depth 16.
linear framebuffer: _________________ | | | | |________________|
tiled framebuffer:
_________________ |__|__|__|__|__|__|__ | |__|__|__|__|__|__|__ | |__|__|__|__|__|__|__ |
when you use tiles you usually need to make allocation in units of full tiles. fixed sized tiles can speed up rendering as tiles probably better utilize the cache and redeuces the amount of framebuffer that has to be processed as only affected tiles need to be updated.
Ahh, thank you Alex and Nicolai, now I am less confused.
Just FYI, R300/R350 chips support 16 pixel square tiling only for zbuffer and colorbuffer, there are also options to have 8 pixel wide and 16 pixel wide tiling - probably for textures, but I can't imagine a situation where we read from textures but do not touch colorbuffer or zbuffer (I assume the limit for zbuffer is also valid for stencil buffer, maybe I am wrong).
By default r300_demo and r300_driver have tiling enabled at 16x16 pixel squares, in fact the card should come up with this on by default..
Now on to the next question - how can one fix the 2048x2048 limit ?
thank you !
Vladimir Dergachev
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