So I have the AMD Radeon HD 7870 Powercolor pcs+ edition and I tried OC this gpu. The default core clock is 925 MHz with boost at 975 MHz and memory clock at 1500 MHz. I downloaded the MSI Afterburner for OC. Then I overclocked the gpu core clock at 1200 MHz with power limit at 20%. Then I runned the unigine heaven benchmark and I see the core clock at 925 MHz and the memory clock at 1376 MHz. After that I reset the settings for the OC in the MSI Afterburner with core clock being at its boost clock, opened again the benchmark and the clocks are always the same. Any help is appreciated.