Official HD 2900 Discussion Thread

[cadaveca]

Basically no one is able to figure out why ATI is using shaders to perform the AA, whilst it is clearly not the way to go due to performance.

Well, at least now ya know the source of "free 4xAA" for DX9 from DX10 cards.

Shaders that would normally be idle during rendering can be used to apply this AA method, however the "thread arbiter" must be programmed for such, and, in most cases, this must be on a per-app basis, until 3Dc kicks in(Three consecutive loadings of the same map will "optimize" the workflow as the driver "recompiles" the workload to what is needed).

This makes alot of sense when apllied to DX9 rendering formats, as it's far easier for the driver programmer to add in the AA for free, and make use of the VLIW format of the gpu, however this can come at a penalty and cause rendering errors if it's not done right. The other option is for the arbiter to pack many instructions at once, and this can cause timing issues far more easily than applying AA to a texture, if a subsequent texture/pixel needs info from data already "in flight" through the gpu.

Problems of a programmable architecture that will only get better over time, IMHO.