PowerTune Analysis

AMD is introducing a new version of PowerTune with the Radeon R9 290 Series.

The card can now measure current via sensors instead of relying on an estimate based on GPU load like in previous generations. PowerTune will take into account GPU temperature, voltage, clock speeds, current draw, and fan speed. A dedicated piece of silicon in the GPU will then decide on a course of action and set new targets, which could result in reduced GPU clock or higher fan speed, or even lower voltage.

NVIDIA's boards have dedicated chips on the PCB that measure the whole card's power consumption, while AMD only measures GPU power consumption, which saves a few bucks per card on power-measurement hardware while still being reasonably accurate.

I did some testing to better understand the new PowerTune feature. The following results were recorded with all settings at default. Time progresses on the horizontal x-axis.



Let me take you through what we are seeing in that chart:

• At the beginning, we find the card idling happily at 300 MHz, with low temperature and fan speed.
• Once we put some load on the card (not Furmark), frequency immediately jumps to 1000 MHz, its full clock speed. There is no delay for some kind of boost to kick in.
• As temperatures increase because of the workload, fan speed will be adjusted accordingly, and clocks will very slowly go down again.
• Once 2000 RPM is reached, which is the maximum fan speed the "Quiet" BIOS allows (to keep noise levels down), fan speed stays the same while temperatures continue to rise. At this point, clocks still hold on to their slow rate of decline.
• Only when GPU temperature reaches 94°C, which is the default temperature limit for both BIOSes, will clocks decrease faster to ensure the GPU doesn't crack the temperature limit.
• Temperature and fan speed stabilize after another while, but clocks only run at a fraction of the 1000 MHz. The card was in our case seen to run as low as 570 MHz instead, which reduced performance greatly. We also found that PowerTune kept on adjusting GPU clock to maximize performance, which is a good thing.

Next, we did the same test using the "Uber" BIOS. All other parameters were the same as in the previous test.

• At first, we see exactly the same behavior: Temperature increases, fan speed follows, and GPU clock is slowly reduced.
• The fan will quickly ramp up past 2000 RPM since this BIOS does not come with the 2000 RPM maximum fan speed limitation. Provided with more fresh air, the card can stay at higher clocks for longer.
• Once the fan reaches around 2500 RPM, we see temperatures stabilize just below the 94°C limit, which is indicative of sufficient cooling for our load at those clocks (900 MHz+).
• At this point, I placed my hand in front of the fan intake to see what would happen with higher loads / cases with worse airflow.
• Temperatures now hit the 94°C limit, which means the GPU isn't allowed to get any warmer. Fan speed immediately increases to handle the increase in heat, and clocks are reduced to curtail heat output.
• As time progresses, we see fan speed increase and clocks decrease, but those adjustments are not as big as with the "Quiet" BIOS. The card is very noisy in that state, though.