FSAA Performance

As we have revealed in our ATI Radeon HD 4850 review, ATI and Nvidia solutions provide very high anti-aliasing quality these days. Since GeForce GTX 200 inherited its FSAA algorithms from the predecessors, it doesn’t make sense to discuss any game screenshots one more time. We suggest focusing on another matter: graphics card performance with enabled FSAA.

Theoretically, Nvidia G200 should easily cope even with the most extreme FSAA modes thanks to 32 RBE units and 512-bit memory access bus. Nevertheless, we have to check it out in tests, before drawing any conclusions.

It makes sense to discuss only 1920x1200 resolution, because in lower resolutions enabling FSAA has minimal influence on the performance except a few extreme modes, such as ATI edge detect CFAA.

Nvidia CSAA modes differing from the classical MSAA only by bigger number of samples on the grid, are pretty liberal when it comes to the video memory capacity and bandwidth. And our results prove it very well. When Nvidia GeForce GTX 280 switches from classical MSAA 4x to CSAA 16xQ, combining MSAA 8x and 16 grid samples, the performance drops only 10%, which is truly impressive. At the same time, ATI Radeon HD 4850 lose just a little more,12%, when switching from MSAA 4x to MSAA 8x. However, it features half the RBE units and has no 512-bit memory bus.

In other words, we see once again that even with smaller resources available one can often achieve very decent results if using these resources in a smart way. Almost as good as in case one simply increased the capacity without introducing any architectural optimizations. The results demonstrated by Nvidia GeForce GTX 260 prove it, too: it lost 18% of speed when switching from MSAA 4x to CSAA 16xQ, although it features a 448-bit memory access bus with 112GB/s bandwidth, which is much higher than by ATI Radeon HD 4850.

All in all, we see that Nvidia’s CSAA algorithms provide an almost ideal compromise between performance and anti-aliasing quality. They barely affect the performance of the new GeForce GTX 200 family, so the owners of new graphics cards shouldn’t ever question using them, while the GeForce 9800 GTX users may want to reconsider even enabling the common MSAA 4x.