Elite Bastards posted a review on the AMD Radeon HD 5870 1GB CrossFire performance

Now we move on to a far more important topic - Real-world game testing. Here, we put both our AMD Radeon HD 5870 CrossFire configuration through its paces under Windows 7 Home Premium x64 in no less than eight current game titles. For the duration, of this article, we'll be catering towards standard sized LCD owners by starting out with a target resolution of 1920x1200, albeit with AMD's own 12x edge detect anti-aliasing mode and 16x anisotropy enabled to make the most of the additional image quality capabilities on show here, before following this up with some far more GPU intensive rendering at 2560x1600 for you 30" LCD owners out there to stress the boards more fully - first without any anti-aliasing or anisotropic filtering, followed by testing with 8x AA and 16x AF enabled.

AMD Radeon HD 5870 1GB CrossFire performance Review