Anti-Aliasing Performance

With the image quality investigation over with, now it's time to look at the performance of all of these AA settings. As usual, the newcomer goes first - let's see how the GeForce FX's performance is impacted by its plethora of AA settings:

Impact of Anti-Aliasing on Performance
NVIDIA GeForce FX 5800 Ultra
Anti-Aliasing Off

2X

QC

4X

6XS

8XS

100%

90%

90%

76%

39%

31%

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0
|
20
|
40
|
60
|
80
|
100
|
120

Just as NVIDIA has promised, both 2X and Quincunx modes are virtually "free" but as we all know, just because something is "free" doesn't mean it's good. Flip back a page to our comparison screenshots and you'll see that neither of these modes does much in the way of actually anti-aliasing, so we turn to some of the higher sampling methods.

Next up we have NVIDIA's 4X mode, which delivers around 3/4 the performance of the FX 5800 Ultra without any sort of AA enabled. As you can see, once you get beyond 4-samples you're reducing the performance of the card to less than 40% of its original capabilities.

Once again we look at the lower clocked GeForce FX 5800 to see how having less memory bandwidth and a lower fill rate influences performance:

Impact of Anti-Aliasing on Performance
NVIDIA GeForce FX 5800
Anti-Aliasing Off

2X

QC

4X

6XS

8XS

100

84

84

66

33

22

|
0
|
20
|
40
|
60
|
80
|
100
|
120

The performance drops are much more pronounced on the regular 5800 as you can expect given the 20% reduction in core and memory clocks.

Impact of Anti-Aliasing on Performance
ATI Radeon 9700 Pro
Anti-Aliasing Off

2X

4X

6X

100%

82%

70%

60%

|
0
|
20
|
40
|
60
|
80
|
100
|
120

With the Radeon 9700 Pro we see that both the 2X and 4X modes take a slightly larger performance hit than the comparable settings on the GeForce FX, but what's truly interesting is ATI's 6X mode. A feature that ATI hasn't done a great job of publicizing is their frame buffer compression algorithm that is enabled only in AA modes, but it does boast a higher compression ratio than NVIDIA's 4:1 color compression algorithm. The benefit of this higher ratio compression algorithm can be seen in the relative performance of ATI's 6X AA setting, it delivers 60% of the 9700 Pro's original performance compared to the GeForce FX's 6XS mode with its 39%.

If you want numbers to quantify this difference, with 4X AA enabled the GeForce FX 5800 Ultra is around 9% faster at 1024x768 than the Radeon 9700 Pro (156.9 vs. 143.8), but switching on 6X AA puts the 9700 on top of the FX by no less than 53% (123 vs 80).

Anti-Aliasing Quality Compared AA+AF Performance

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