Skyrim AMD CrossFireX Performance and IQ Review

AMD has provided a new Catalyst 11.11b Performance driver that supports CrossFireX in Skyrim for Radeon HD 6000 series owners. We will evaluate CrossFireX performance, scaling, and see how it compares to the competition. We will also look at FXAA and Transparency AA image quality comparisons.


Radeon HD 6970 CrossFireX Highest Playable Settings

Finding the highest-playable settings with Radeon HD 6970 CrossFireX was not an easy task. We found 8X MSAA and FXAA to work well and performance with that enabled was more than playable. Moving up the quality even further however, was mostly problematic. AMD video cards have the option to enable a Transparency Anti-Aliasing technique which AMD calls Adaptive Supersampling. This is basically a toggle in Catalyst Control Center which allows you to turn on Supersampling AA for alpha textures in games. The level of Transparency SSAA enabled relies on the amount of MSAA you have applied. In this case, with 8X MSAA turned on in the game, 8X AD SSAA is turned on. We found this level of AA to not be playable on Radeon HD 6970 CrossFireX. Performance was horrid, and the game was extremely laggy. This is odd to us, since NVIDIA GeForce GTX 580 SLI is able to play at 8X MSAA plus its special 8X TR SSAA option.

The reason why it is odd is because the GTX 580 has less RAM available per GPU than Radeon HD 6970 has. In GTX 580 SLI both GPUs have access to 1.5GB of RAM. However, with Radeon HD 6970 CrossFireX both GPUs have access to 2GB of RAM. Since performance is above 60 FPS with 8X MSAA and FXAA at 2560x1600, turning on Adaptive Supersampling should be playable, it shouldn't fall to the levels it does. Our graph below shows this.

AMD Radeon HD 6970 with 8X AA and Adaptive SSAA and FXAA

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As you can see, when we turn on Adaptive SSAA with AMD Radeon HD 6970 CrossFireX, performance drops below 30 FPS, and is completely unplayable. However, the GTX 580 SLI with 8X MSAA + FXAA + 8X TR SSAA is able to maintain an average near 60 FPS! The Radeon HD 6970 CrossFireX setup shouldn't be this slow, but all we can think of is that CrossFireX is not working like it should with Adaptive AA in this game.

In trying to figure out what might be causing this, we tried several other settings. Firstly, we disabled FXAA thinking that might be why it's so slow, so the graph below shows 8X MSAA + Adaptive SSAA but NO FXAA.

AMD Radeon HD 6970 with 8X AA and Adaptive SSAA and NO FXAA

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Even with FXAA turned off on the Radeon HD 6970 CrossFireX setup, the game is still not playable with 8X MSAA and Adaptive SSAA only. FXAA wasn't holding back its potential.

Next up, there is another option you can use in Catalyst Control Center, you can reduce the quality Adaptive AA to Multisampling. Multisampling should be faster, but it won't have near the image quality that Supersampling has. So we tested that.

AMD Radeon HD 6970 with 8X AA and Adaptive MSAA

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Performance definitely improved with Adaptive MSAA. However, even with this improved performance, the game was still incredibly laggy and choppy. Even though the performance shows it above 30 FPS here, we cannot call the gameplay experience playable, it just wasn't an enjoyable experience with how laggy it was. So that setting wasn't playable either.

AMD Radeon HD 6970 with 4X AA and Adaptive SSAA

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The only other thing we could do to try and get playable performance with Adaptive SSAA was to turn the AA level itself down. In the graph above, we have turned the in-game AA down to 4X AA, we have no FXAA turned on and Adaptive SSAA is turned on, which will also be operating at 4X level now.

This is what it took to get playable performance. There was still some lag every now and then, the experience wasn't as smooth as the GTX 580 SLI setup, but it was what it took to get it to mostly playable levels with Adaptive SSAA turned on. Whereas, GTX 580 SLI is running at 8X MSAA + FXAA + 8X TR SSAA and is still faster.

GeForce GTX 580 SLI Maximum AA Settings

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Here is a full graph of the run-through on the GTX 580 SLI at 8X MSAA + FXAA + 8X TR SSAA so that you can see that the game was playable through the whole run-through at these very high settings.