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Increasing AA Led to Faster Framerate? How is this Possible?

M

Mister Dark

Member
Right now Half-Life 2 is my favorite game to play, so I'm always trying to optimize my system to get the most out of it for HL2. I've been using the CounterStrike Source Video Stress Test as an easy way to check my frame rate with the Source engine. Just to see how far my frame rate would drop, I tried raising AA from 4x to 6x.

With 4x, I was getting about 108 FPS. With 6x, I got 116 FPS .... Thinking this had to be a mistake, I ran it again several more times - and got the same results each time. How can this be?

My specs: Athalon 64 3000, one gig PC 3200 ram, BFG 6800 OC card w/pipes unlocked, Raptor 10,000 RPM SATA HD ...

I'm running at 1024x768, advanced settings on high, water reflection set to World, 8xanistropic(sp?) vsync disabled ...

Am I really getting 8 more frames a second by raising AA or am I getting false results with the stress test? It would be great if I could bump AA in an actual game of HL2 and see my frame rate INCREASE ...
 
So my video card is faster than my processor -why would giving my video card more work to do speed up my frame rate? That still doesn't make sense to me.
 
In a real game, you will not get an increase in frames with higher AA and the same other settings. The stress test isnt pretty worthless for benchmarking.
 
So, in a real game, will I see a decrease with higher AA? And why is the stress test worthless, Ackmed? What is the best way to benchmark HL2? I tried a HL2 benchmark program, but it screwed up all my settings - changed everything around even when I wasn't using it and I lost in-game sound ....
 
No you won't even see a decrense in fps with higher aa, but look for the aa when you try to run hl2 at x6aa on your geforce and then you will understand why you got more fps.
 
If I play HL2 at 6xAA I will understand why I got more FPS on the Source Test? What exactly am I supposed to see that will explain this to me?
 
nVidia doesn't offer 6xAA with their GF6 series, so when you enable it in-game, you're probably still getting 4xAA. An 8fps difference is probably within the margin of error of that benchmark.
 
I've heard that the GeForce series default back to 0xAA when you select 6xAA. Could be the reason.
 
Maybe so, Pete. But it is a remarkably consistent margin of error - i.e. every time I change to 6xAA I get the 8 frame increase and every time I change back I lose 8 frames ... But your response makes me wonder: if my 6800 doesn't do 6xAA, maybe when I select that option in the Stress Test it defaults back to NO AA? Which is why I see the consistent increase? I'll have to try turning AA off and see what I get then ...Yep. That's what's happening. I tried the Source Test with AA set to none and got 116 FPS - same as I get with AAx6. Then I tried AAx2 and got 113 FPS ... Meaning 6xAA = NoAA with my card (sigh.) Oh well.

EDIT - posted right after Elfear came up with the same answer ... You are right, Elfear.
 
Here is my guess. Maybe the game enabled some level of aa above 2x and when u enabled it in the driver, it disabled the game setting and then set the 2x in the driver to be the dominant decision in the game.
 
Yup, running 6xAA (which isn't supported on NV40 cards) is probably running at 0xAA.

But now to throw something else into the mix: it's a fact that sometimes running 4xAA instead of 0xAA is actually faster on NV40 cards. I have personally verified this in a range of different games and benchmarks (e.g. SOF2, EF1, EF2, etc).

I'm currently at a loss to explain this except maybe that a driver bug is crippling peformance when 0xAA is used. Or maybe certain kinds of optimizations are not available when no AA is being used.

But hey, I'm not one to complain when cranking IQ increases performance. 🙂
 
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