Antialiasing
The Radeon X800's antialiasing hardware hasn't changed significantly from the Radeon 9800 XT, but ATI does have a few tricks up its sleeve. Let's start with a look at traditional multisampling edge AA, which ATI and NVIDIA do fairly similarly.

The X800 cards' AA performance is about what one might expect. The big news here, believe it or not, is the 8X AA mode from NVIDIA. The 6800 Ultra is performing much better than it did in 8X mode with older drivers.

Let's have a look at the AA sample patterns to see if we can discern why. Remember, green represents texture sample points, and red represents geometry sample points.

2X 4X 6X/8X
GeForce FX 5950 Ultra

GeForce 6800 Ultra

Radeon 9800 XT

Radeon X800 XT

The X800 doesn't vary from the path taken by its predecessor, with the same stock sample patterns for 2X, 4X, and 6X modes. The GeForce 6800, though, has a new sample pattern for both 4X and 8X AA. In fact, the 8X mode is now identified in NVIDIA drivers as "8xS" mode, and it's a new pattern from the one we saw in our initial review of the GeForce 6800 Ultra. The fact there are only two geometry sample points suggests that NVIDIA's new driver has enabled a 2X supersamling/4X multisampling mode, replacing the 4X supersampling/2X multisampling method we saw earlier. That explains the performance jump in 8X mode for the GeForce 6800 cards, because multisampling is more efficient.

That's progress for NVIDIA, but ATI's sparse sampling pattern for 6X AA is not aligned to any kind of grid, making it very effective in practice. Also, ATI's cards use gamma-correct blending to improve results. When we interviewed Tony Tamasi of NVIDIA recently, he said the GeForce 6800 is capable of gamma-correct blends, as well, but we've since confirmed that the feature won't be enabled until a future driver release.