OverclockingTo find the maximum overclock of our card we used a combination of ATITool's successor and our benchmarking suite.
The overclocks listed here were achieved with the default fan and voltage settings as defined in the VGA BIOS. Please note that every single sample overclocks differently, that's why our results here can only serve as a guideline for what you can expect from your card.
The final overclocks of our card are 825 MHz core (10% overclock) and 1120 MHz Memory (38% overclock). There is nothing spectacular with the core overclock, it still allows for some fast and easy performance gains. The memory overclock is simply stunning. When I first saw the default memory clock I wondered "O_o 800 MHz GDDR5? Does anybody even make such slow chips?". Our sample came with memory chips that are guaranteed to run at 1000 MHz + unofficial overclocking potential. In the end we could overclock the memory by 38% (!!!) which can be attributed to the nice memory chips that AMD uses.
Possible reasons for the low default memory clock:
- Board power consumption. As you read on the power consumption page it is not possible to downclock the memory in idle. Higher clocks would result in a higher idle and load power consumption.
- Sales. AMD would lose volume on their HD 4830, HD 4850 and HD 4870.
- Stability. I also noticed during overclocking that sometimes during a clock increase the card would just crash with a garbled screen, even though that memory clock is perfectly stable. Future BIOSes can most probably fix this problem.
Overclocked PerformanceUsing these clock frequencies we ran a quick test of Call of Duty 4 to evaluate the gains from overclocking.
The actual 3D performance gained is 16.8%.
Temperatures are in a perfectly safe range, I would have wished for less fan noise and slightly higher temperatures though.