FSAA Performance

Finally, we'll take a look at 6800 Ultra's rendering performance with FSAA under a few different scenarios.

Here we are looking at the same SS:SE test at 1600x1200, as this represents on of the few resolutions there is actually any kind of limitation from the graphics board as opposed to the rest of the test system used.

Here we see that the 2X modes take very little performance away from normal rendering, except when 16X AF is enabled. 4X FSAA is having a slightly larger hit with no AF and 8X AF, but curiously a slightly smaller performance impact with 16X AF enabled. In all mode 8X AF takes quite a large performance hit because it is a combination of 4X Super-Sampling and 2S Multi-Sampling, which will reduce the effective fill-rate by a quarter.

Pure Multi-Sampling FSAA (MSAA) is all calculated in the ROP's, and is separate from Pixel Shader engines. Theoretically MSAA and Pixel Shader can work without any performance impact as MSAA is mainly a bandwidth intensive task, while shader operations are more maths bound so they will burn clock cycles without using much bandwidth. We can put this to the test by looking at the FSAA performance under the Phong Lighting test in RightMark.

As you can see, all the pure MSAA modes are coming through with virtually no performance penalties, which is as we expected. 8X FSAA does drop to a quarter of the original performance because the Super Sampling element cuts the fill-rate in quarter and 4 times the amount of shader calculation is occurring.

Finally we'll take a look at the FSAA performance in the more varied rendering environment of 3DMArk03's GT2 test.

In this instance we can see that FSAA is taking a much larger performance hit than we have seen in many of the game tests, with the 2X modes reducing rendering performance from normal rendering by about 22%, 4X 44% and 8X 88%.