Lastly, when switching over to Unigine Heaven, which is the most demanding Linux tech demo available from Unigine Corp, the RV770-generation of ATI graphics processors were actually faster than the Radeon HD 5700 and Radeon HD 6800 series. The GeForce GTX 460 was also faster. Why? Well, Unigine Heaven is buggy for the Radeon HD 6800 series with some Catalyst driver versions, including the fglrx 8.83 build.
Fortunately, there are Unigine Heaven fixes coming in fglrx 8.84 to hopefully clear up the Radeon HD 6000 series performance issues with this demanding OpenGL benchmark.