Half-Life 2: Episode Two
We used a custom-recorded timedemo for this game, as well. We tested Episode Two with the in-game image quality options cranked, with 4X AA and 16 anisotropic filtering. HDR lighting and motion blur were both enabled.
The 4870 X2 isn't quite as fast as a two-card 4870 CrossFire config here, but it's close, running only a handful of frames per second behind at 2560x1600. Compared to the X2's intended target, the GeForce GTX 280, it's not even close. This game scales nicely with multi-GPU setups, and the X2 takes a decisive lead over the GTX 280.
Of course, the GTX 280 also churns out over 65 frames per second at the highest settings tested, so we're not talking about huge differences in competency when running this game.