Because we know that the RV770LE graphics processor is really a Radeon 4850/4870 graphics processor that’s been underclocked, we have high hopes for the Radeon 4830 when it comes to overclocking.
We like the convenience of the Catalyst Control Center’s Overdrive overclocking tool, but we have to admit we’re not big fans of the top speed limits set by the utility. Therefore, we went ahead and installed Ray Adam’s Tray Tools utility, which offers a lot more overclocking flexibility.
Starting with PowerColor’s 4830 card, we increased the core clock until we started to get video driver crashes. It was fine all the way up to 785 MHz, which is more than a 200 MHz overclock from the stock speed of 575 MHz. This is with no voltage increase whatsoever--just a simple clock increase. We backed it up a notch to represent a speed at which we would be comfortable running the card 24/7 and settled on 765 MHz.
The memory wasn’t quite as accommodating as the core, giving us an extra 90 MHz before showing artifacts. We settled on a 980 MHz clock speed for the memory, yielding a final overclock of 765 MHz core/980 MHz memory compared to the stock 575 MHz core/900 MHz memory.
With expectations of similarly scalable clocks, we installed the Sapphire 4830 to see what it could do. To our chagrin, the Sapphire card wasn’t compatible with Tray Tools, so we were forced to stick to AMD’s Overdrive utility. We still managed to pull an acceptable 690 MHz from the core, and we found the card’s memory to be even more accommodating by overclocking to 1, 080 MHz, which is 100 MHz more than the PowerColor card offered–-and without the PowerColor’s memory heat spreaders no less (which may have been more of a hindrance than a help) .
After overclocking the PowerColor and Sapphire cards, we re-benchmarked Crysis at the High detail setting to compare the two cards when overclocked, the reference 4830, and the factory overclocked GeForce 8800 GT:
At High details the factory overclocked GeForce 8800 GT bested the reference 4830, but the overclocked 4830s sailed past for the win. In the case of the PowerColor 4830, the difference between the reference speeds resulted in a 10 FPS increase, which is over a 30% gain in performance. Even the Sapphire overclock was highly respectable, leading us to conclude that even when the conditions aren’t ideal, the Radeon 4830s are a good overclocking prospect.