ATI Crossfire support

[Brian]

Hello,

I get no performance gain with Crossfire in the Video card benchmarks. This seems slightly strange to me, as most games do run better.

Is this because your app is not coded for Crossfire, or because the Crossfire drivers do not support your app for Scissors rendering?

Just curious, as I am always trying to better my score.

-Brian

[David (PassMark)]

We haven't looked at ATI CrossFire in great detail as yet. But my feeling is that is probalby only works for full screen 3D apps and like nVidia's SLI solution there is a hard coded list of games in the device driver, and if an application isn't on the hard coded list, CrossFire does nothing. (With SLI however, there was a tool that you could add new apps to the list, at your own risk).

On the ATI (now AMD) web site they have a list of games supported but at the same time they claim to support all games. Which doesn't make a great deal of sense. They also claim that, "Some applications that are more CPU intensive may not scale well with multi-GPU solutions. For these applications, CrossFire offers extreme image quality modes that take advantage of the additional graphics power". But then go on to claim that, "CrossFire enables performance gains in all 3D applications".

Plus they also suggest, "In the rare event that the an application hasn't yet been profiled in Catalyst Control Center, additional performance gains in the majority of titles can be achieved by setting the Catalyst A.I. setting to 'aggressive'."

So maybe ATI haven't, 'profiled' PerformanceTest and you need to make some adjustments in the control panel.

[Brian]

I have read several articles about Crossfire. Here is what I found out if anyone else is interested in it.

Crossfire is different than SLI, in the respect that it will work with every DX9 title, however if no profile is defined within the drivers. The system will use SuperTiling. Which yeilds about a 115% output compared to one card. So +15% performance gain on every DX9 Game or Application.

So unless the profile is added to the driver there will not be a significant increase in FPS, if the profile is added, and the games sets to Alternate Frame Rendering. There could be as high as double the performance of one card. However, depending on how they wrote the game, this may not be possible.

ATI drivers will dynamically pick profiles for you, which is good. However, the down side is that you cannot create profiles for games to follow. You get what you get.

So I guess it is more upto ATI to add the correct profile for your benchmark, then you coding for it.

-Brian