Measuring the Power Draw
The following diagrams contain a text header, which is followed by the actual measurement curves. In that header, you'll find the average and peak power draw on all three rails, along with the sum of those averages, giving us the total average and peak power consumption.
Total peak wattage is not simply the sum of the three individual peaks, but rather the total peak wattage observed within the 120-second sample window. That makes more sense than adding the peak wattages together, since it's unlikely that all three max out at the same moment.
Power Consumption during Gaming
These diagrams employ a logarithmic scale. The thick red line represents average total power draw at a time resolution of six seconds.
The average power consumption demonstrated by PowerColor's PCS+ R9 290X is 262 W, in line with what we expected. That's 3 W higher than the 30 MHz-faster MSI R9 290X Lightning. Approximately half of a watt can be attributed to the PowerColor card's memory, which operates at 1350 MHz, rather than 1250 MHz. But a few watts could be lost by less complex voltage regulation circuitry.
Still, the differences are small. And while the PCS+ R9 290X may exhibit slightly higher power use, it also pulls about 10 W less from the motherboard slot than MSI's card.
Power Draw During Internet Surfing
People don’t spend all of their time gaming; typically, much more is spent browsing the Web. We simulate this workload with a static version of our home page, scrolling all the way down and back up again. While scrolling does make use of hardware acceleration, the power draw for that is quite benign.
Power Draw at Idle Load
Many people leave their PCs on all the time, making the power consumption of components at idle quite important. Measuring draw from the wall doesn't cut it if we want to isolate the graphics card, since there's no way to reliably factor out the rest of the platform.
Our state-of-the-art test equipment shows that this graphics card only draws 13.7 W at idle, which is less than our previous generation of lab instruments indicated: