Overclocking

The Radeon HD 2900 XT still uses the dreaded 2D/3D clocks to save power when the GPU is not needed for 3D operations. In 2D mode the core runs at 509 MHz, the memory at 511 MHz. The GPU voltage is at 1.00V. Once you run a full-screen application, the driver will change the clocks to 739 MHz core and 819 MHz memory, the GPU voltage is also increased to 1.15V.

Since ATITool does not work to change the clocks we had to use several different applications (which unfortunately we can't show you) to do some overclocking. Overclocking should be possible using the CCC Overdrive module, but the maximum clocks will be limited. ATITool Scan for Artifacts works, but you can't change clocks, we have an early version now that supports monitoring and voltage changes.



The overclocks are quite ok for a brand new product. In the end the card runs totally stable at 850 MHz core (14.5%) and 970 MHz memory (17.5%).

As I am told the BIOS will check the presence of an 8 pin power connector on bootup. If it is not connected, Catalyst Control Center will not allow any clock changes. This is done to ensure that enough power is delivered to the GPU. Personally I find this will drive many users away from CCC to other tools that can do it without such a limitation. Actually, I wasn't able to verify that CCC does indeed appear because I don't have any 8 pin PSUs yet.


The stock cooler tends to be a bit noisy when running 3D apps at full load, especially at higher clocks. Even with the cooler running fairly fast we saw temperatures of 58°C in idle, 72°C under load and 80°C under load with overclocking. With ATITool you can raise the fan speed, but the fan running at 100% sounds like a leaf blower.


Software can change the voltage, and all the extreme overclockers will be happy that you can go up to 2.035 V on VDDC (1.00 V default), MVDDC max. 3.400 V from 2.20 V default and MVDDQ up to 2.482 V from 1.897 V default.


While playing with voltage changes and trying to find maximum overclocks I got to a point where even the fan running at 100% could barely keep the card cool, the system was pulling measured 470 W from the main AC line. This was at 1.36V VDDC (GPU Core Voltage), in my opinion anything above 1.30V is way too much for the stock cooler to handle. Even at such an insane voltage I could "only" get 911 MHz on the GPU. There definitely seems to be a use for more extreme cooling solutions. Our friend Kinc has his card running at above 1100 MHz using extreme cooling and crazy GPU voltage (set with ATITool of course).