The Unigine Engine is currently the most demanding game engine that is natively available for Linux. With the older Unigine Sanctuary tech demo, at 2560 x 1600 the Radeon HD 6870 is above 60 FPS. While not directly related to the Radeon HD 6870, the benefits of using CrossFire under Linux remain virtually non-existent. As these results are showing from the Radeon HD 4870 X2, when CrossFire is enabled and the chains are setup via aticonfig, still in nearly every Linux OpenGL test there are not quantitative gains associated with the two RV770 GPUs as the system's disposal.
The Radeon HD 6870 with Unigine Tropics at 1920 x 1200 was running at 85 FPS, which was 60% faster than the Radeon HD 5770.
When upping the resolution to 2560 x 1600 for the Unigine Tropics test, the Radeon HD 6870 still could cope with the greater workload where its frame-rate was hovering around 60 FPS.