OverclockingTo find the maximum overclock of our card we used a combination of GPUTool and our benchmarking suite.
The overclocks listed in this section 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 overclocks of our card are 955 MHz core (2% overclock) and 1550 MHz Memory (9% overclock). While the core overclock may look slim, you'll have to consider that PowerColor already overclocks the card out of the box which will heat into overclocking margins. Compared to other HD 6970 cards the maximum clock potential is nicely increased, on the AMD reference HD 6970 we saw only 915 MHz maximum clock. Memory is overclocking fine, too.
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 from overclocking is 5%.
Temperatures are low in all configurations, I'd rather prefer an optimized fan profile with less noise and slightly higher temperatures.
Voltage TuningIt has been a long known fact that overclocking headroom increases as soon as you increase the operating voltage. Until recently, software voltage control on VGA cards has been the exception and most users were not willing to risk their warranty by performing a soldering voltmod. Nowadays almost all current graphics cards have voltage control in order to achieve low power consumption by lowering voltage when in idle or slightly loaded.
In this section we will increase the GPU operating voltage step by step and record the maximum clock speed possible. Voltage is listed as the value that the voltage regulator reports via software, not actual measured voltage. The card was installed in-case, with fan settings at the default, memory will not be overclocked either. If a card has thermal throttling we will reduce the operating frequency to keep performance at maximum for a given voltage. Please note that the fan profile will have an effect on observed temperatures: if the card gets hotter the fan will ramp up to reduce temperatures or keep them from rising fast.
The following graph shows the overclocking potential we saw on our sample. GPU clock is represented by the blue line, which uses the vertical clock scale on the left. The scale starts at the default clock to give a feel for the overclocking potential over the base clock. Temperature is plotted in red using the °C scale on the right side of the graph. An additional graph shows the full system power draw in orange measured at the wall socket when running at the given voltage, clock & temperature.
PowerColor's HD 6970 PCS+ gains nicely with voltage, easily leaving the 1 GHz mark behind. Once it approaches 1015 MHz at 1.4 V the gains stop, probably because of all the heat from the extra juice - the cooler does handle the heat fine, though.
Clock ProfilesModern graphics cards have several clock profiles that are selected to balance power draw and performance requirements.
The following table lists the clock settings for major performance scenarios and the GPU voltage that we measured. We measure on the pins of a coil or capacitor near the GPU voltage regulator.
|Desktop||250 MHz||150 MHz||0.92 V|
|Blu-ray Playback||500 MHz||1425 MHz||1.20 V|
|3D Load||940 MHz||1425 MHz||1.24 V|
|CCC Overdrive Limits|