To overclock the reference Palit 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.
The utility then runs an automated clock configuration on each GPU to determine the highest core and memory clock frequency that is stable.
We started out at 750MHz on the core and 900Mhz on the memory, but was able to reach 790MHz on the core and 1090Mhz on the memory. This is a 40MHz overclock on the core and 90MHz on the memory. This is actually a slightly better overclock than the Radeon HD 4870 that we reviewed a couple months ago.