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Old 11-28-10, 12:02 AM   #45
Vardant's Avatar
Join Date: Apr 2009
Location: EU
Posts: 1,041
Default Re: ATi benches inflated by reduced AF

You don't think testing an unreleased product with drivers, that probably aren't even available to public is grasping straws?

Too bad, NVIDIA already commented on this.
Hi Everybody,

What is being experienced is not an “Antialiasing cheat” but rather a HawX bug that is fixed by our driver using an application specific profile.

In a nutshell, the HawX application requests the highest possible AA “sample quality” at a particular AA level from our driver. Without our driver fix, the game would be running 16xCSAA instead of standard 4xAA when you select 4xAA in-game. It runs the proper 4xAA with the driver fix. You defeat the fix by changing the .exe name, causing it to run at 16xCSAA.

You may remember that Geforce 8800 introduced Coverage Sampling AA (CSAA) technology, which added higher quality AA using little extra storage. Prior to 8800 GTX and CSAA, there was only one “sample quality level” for each AA level, so if an application requested four AA samples, the hardware performed standard 4xAA. However, with 8800 GTX GPUs onwards, our drivers expose additional sample quality levels for various standard AA levels which correspond to our CSAA modes at a given standard AA level.

The “sample quality level” feature was the outcome of discussions with Microsoft and game developers. It allowed CSAA to be exposed in the current DirectX framework without major changes. Game developers would be able to take advantage of CSAA with minor tweaks in their code.

Unfortunately, HawX requests the highest quality level for 4xAA, but does not give the user the explicit ability to set CSAA levels in their control panel. Without the driver profile fix, 16xCSAA is applied instead of standard 4xAA. Recall that 16xCSAA uses 4 color/Z samples like 4xAA, but also adds 12 coverage samples. (You can read more about CSAA in our GeForce 8800 Tech Briefs on our Website).

When you rename the HawX.exe to something else, the driver profile bits are ignored, and 16xCSAA is used. Thus the modest performance slowdown and higher quality AA as shown in the images.

To use “standard” 4xAA in a renamed HawX executable, you should select any level of anti-aliasing in the game, then go into the NVIDIA Control Panel and set 4xAA for “Antialiasing Setting” and turn on “Enhance the application setting” for the “Antialiasing mode”.

Nick Stam, NVIDIA
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