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 848 MHz core (8% overclock) and 1172 MHz Memory (17% overclock). This overclock is decent, especially the maximum memory clock has increased nicely compared to the GTX 480 and is now almost on par with what AMD's latest memory controller can achieve. Compared to the NVIDIA GTX 580 reference board that we reviewed last week the maximum core clock is about 10 MHz higher, while memory is unchanged.
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 7.4%.
Temperatures seem to be well optimized as NVIDIA claims. A little higher idle temperature for less idle fan noise would be something I'd prefer, but overall the temperature looks good. (Tested with Crysis, not Furmark).
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.
Up to around 1.125 V the card responds well to voltage but the fan speed increased substantially. Once we reached 97°C the card started to throttle down which forced us to lower clocks to reduce power consumption to get out of the throttling state to maximize performance.
ASUS also includes their Smart Doctor utility with the card which allows voltage changes up to 1.21 V which should be more than enough for most users given the results above.
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||51 MHz||68 MHz||0.96 V|
|Blu-ray Playback||405 MHz||162 MHz||0.96 V|
|3D Load||782 MHz||1002 MHz||1.05 V|