To overclock the Sapphire HD4870 2GB Vapor-X edition I started out with ATI's Catalyst Control Center and used the Overdrive tab to increase the GPU and memory clock speeds as well as bumping the fan speed to 100% for the most potential benefit. The core clock speed maximum in the CCC was 800MHz so that seemed like the logical point to start at. The Vapor-X card did this with ease and did not fail in benchmarks or with Futuremark. Since the CCC was limited in the clock speeds that could be set, I next moved to Riva Tuner 2.24 to push the clock speeds higher than the CCC would allow. I pushed upward until I was no longer able to successfully complete gaming tests or pass benchmarks. The maximum where I could run some but not all of the benchmarks was 845MHz on the RV770 core. But with that said, I had to back down the clock speed to 826MHz on the core and 1086MHz on the GDDR5 memory to get full game and benchmark stability back. I was hoping the added cooling capability would offer a significant boost in clock speeds, which is something I did achieve with an increase of 77MHz on the core and 186MHz on the memory all while having a nice cool running card to boot. Maximum temperatures noted while running a 100% fan speed was 58 Celsius.