It's been a busy week and I haven't had much time to devote to testing. I did however, run a few tests using the S.T.A.L.K.E.R.: Clear Sky benchmark. The benchmark does not require that the game be installed and can be downloaded for comparison purposes.
The benchmark is based on one of the in-game locations – Marshland. The testing process includes four stages, those utilizing various weather and time of the day settings (day, night, rain, bright sun). In order to test your system thoroughly the benchmark is provided with a number of presets and options including different versions of DirectX (9.0, 10.0, 10.1), screen resolutions, antialiasing etc, all at your disposal.
The results are based on DirectX 10.
Average frame rate looks good. Somewhat concerned with minimum frame rate.
Default Setting - 1680, 1920, and 2560
High Setting - 1680, 1920, and 2560
Extreme Setting - 1680, 1920, and 2560
Links to other Radeon 5870 reviews that used the S.T.A.L.K.E.R.: Clear Sky benchmark: