To overclock the HIS Radeon HD 4870 graphics card, we used ATI Overdrive that is part of the CATALYST Control Center. When you ‘unlock’ the ATI Overdrive, you can manually set the clock and memory settings or let the ‘auto-tune’ utility to set the frequencies for you. Just for fun, I tried out the auto-tune feature to see if it could really find a stable clock configuration and it worked in just a few minutes and did not lock up the system.
We started out at 750MHz on the core and 900Mhz on the memory, but was able to reach 780MHz on the core and 1090Mhz on the memory. This is a 30MHz overclock on the core and 190MHz on the memory. The core overclock was not too impressive, but the slider in the CATALYST Control Center (CCC) only goes up to 790MHz. This is the first time we have used GDDR5 memory and the Qimonda IC’s that ATI uses impressd us by overclocking 190MHz! The memory went from running 3600MHz to 4360MHz, which is awesome! That is a 21% improvement in memory clock frequency by using Auto-Tune!
Just for fun we fired up 3DMark Vantage to see how overclocking impacts performance and found that the overclock boosted performance by 6.6% on the GPU test. Not too impressive, but it is still a boost in performance. The minor 4% core overclock is the limiting factor here!