Anisotropic Filtering and FSAA Performance

Here we'll look at the performances of the other models of Anisotropic Filtering and FSAA available on the GeForce 7800 GTX using 3DMark03's Game Test 2.

In this case there is only an 8% performance drop from 1x to 16x Anisotropic Filtering, with the largest drop from 2x to 4x AF.

The performance degradation for the AntiAliasing modes is somewhat larger, and inline with previous boards. For 2x FSAA the performance drop is likely due to the increased bandwidth demands for two samples per pixel, as opposed to one. The maximum number of samples handled in a single cycle is 2, so the 50% performance hit for 4x FSAA is possibly related to that as each pixel needs two cycle to write - if the test was more dependant on shader operations, hence more time being spent processing internally over the shader ALU's, this cost would decrease. The performance is further decreased with 8x FSAA as this is a mixed Super and Multi-Sample mode which requires two full passes through the shaders as well as two cycles for each pass for each pixel.

With 16x AF enabled each of the AA modes have roughly the same performance drop as without AF, in this test, albeit from a lower performance standpoint in the first place.