To overclock the ATI Radeon HD 4850 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 625MHz on the core and 993Mhz on the memory, but was able to rech 690MHz on the core and 1088Mhz on the memory. This is a 65MHz overclock on the core and 95MHz on the memory. That adds up to about a 10% overclock, which is not bad!
When it came to the GeForce 9800 GTX+ we overclocked it manually using the EVGA Precision overclocking utility. We were able to reach 840MHz with full stability and had the shaders locked in at 2084MHz. The memory was able to be overclocked from 2200MHz to 2430MHz, which was also a nice increase.
If you recall from our 3DMark Vantage test page the stock clocks scored 7888 with Physics enabled. After the overclock the score increased nearly 1,000 points up to 8,862 3DMarks (a 12.3% increase in performance)! The card would run at 900MHz on some benchmarks, but wasn’t stable on others like 3DMark Vantage. We stopped at 840MHz on the core and 1215MHz on the memory, but this card may have a little more in it. Notice the card was running 50C with these settings!
UPDATE 6-20-2008: We spent another couple hours overclocking the card and managed to get the NVIDIA GeForce 9800 GTX+ higher with full stability. We manged to get it up to 855MHz on the core, 2200MHz on the shaders and 2550MHz on the memory ICs by un-locking the core and shader frequency lock. This improved performance as you can see below. After doing these last few increases the overall score jumped up to 9,211 3DMarks, which ends up being a 16.7% performance increase! That score is just 500 points away form the GeForce 9800 GX2!