Using the MSI AfterBurner overclocking utility, we were able to push the core clock of both graphics cards up to 1020MHz. The memory of the HIS 6870 worked at 1200MHz and the 6850 reached 1150MHz.
Our manually overclocked HIS Radeon HD 6870 IceQ X Turbo X produced 12% better performance in Call of Duty: Modern Warfare 2 than the factory-overclocked configuration. However, the HIS Radeon HD 6850 IceQ X Turbo was just 6% faster once the maximum stable overclock was applied.
The HD 6870 IceQ X Turbo X was just 2% faster in Crysis Warhead once we overclocked further, while the HD 6850 IceQ X Turbo was 14% faster.
When testing the maximum stable overclocks in Battlefield Bad Company 2, we found the HD 6870 IceQ X Turbo X was 6% faster. The HD 6850 IceQ X Turbo has more ample gain room as it received a 14% performance increase versus the factory overclock.