RADEON X800 Pro: Extreme Overclocking
You can refer to my PowerColor RADEON X800 Pro review for details about modification and extreme overclocking of this graphics processor. This time the graphics card had a water-cooling system on instead of the standard cooler. The diagram below shows you the power consumption results as measured at the card’s regular frequencies with the nominal voltages as well as at overclocked frequencies with Vgpu adjustment:
During extreme overclocking, the power consumption of the graphics card grew up by 48.9% in the Idle mode and by 66.9% in the Burn mode (the GPU frequency growth was 32.6%, the memory frequency growth was 31.1%).
Curiously enough, the power consumption of the card at the nominal frequencies turns to be lower with the water-cooling system than with the standard air cooler. Evidently, the water leads to a lower GPU temperature, thus positively affecting the power consumption. This is probably due to the reduction of various leakage currents and other effects when the die temperature is low – specialists in semiconductors may have something to add on the topic. I can only show you a diagram from the report on extreme overclocking of the RADEON X800 Pro – it contains the die temperature and the ambient temperature:
But back to the power consumption – it grew up to 78 watts at extreme overclocking!
The next diagram shows the dependence of the power consumption on the GPU frequency and the GPU voltage. Note that we have only the core frequency increasing, while the memory is left on the nominal clock rate. That’s why the power consumption is lower than at the simultaneous overclocking of the core and memory.
Up to 535MHz core frequency, the GPU voltage remained the same and the card worked with its standard cooling system. The power consumption was growing up in a direct proportion to the core clock rate.
At 550MHz and 560MHz frequencies, the core voltage remained the same, but I installed a water-cooling system. The power consumption then went down somewhat.
To increase the GPU clock rate further, I had to increase the GPU voltage. The power consumption started going up, and at a higher rate than at ordinary overclocking. However, the power consumption and the core voltage remained in a linear proportion: 3-4 Watts for each extra 10MHz of core frequency and 0.05v of core voltage.
So, extreme overclocking with voltage modification is the best way to check your system for reliability. You shouldn’t experiment with volt-modding without having a PSU reserve, a good cooling system on the graphics card and a clear goal before you.