Idle Power Consumption Results
Power Consumption: Idle (2D Desktop)
Unfortunately, AMD doesn’t fare very well here. We’ve repeated these measurements, reviewed running processes, and even switched systems altogether. We just couldn’t get the Gigabyte Windforce Radeon R9 285 to draw less than 15 W at idle.
Looking at just one minute’s worth of power draw curve after smoothing it over a bit, it’s plain to see that there are significant fluctuations even at almost 0 percent load.
The situation at the motherboard slot looks perfect. We never exceeded or even reached 75 Watts.
Let’s take a look at how that 15 W idle draw is distributed:
| Header Cell - Column 0 | Minimum | Maximum | Average |
|---|---|---|---|
| PCIe 12V | 2 W | 21 W | 8 W |
| Motherboard 3.3V | 1 W | 3 W | 2 W |
| Motherboard 12V | 0 W | 31 W | 5 W |
| Graphics Card Total | 2 W | 45 W | 15 W |
List of All Individual Values per Supply Line
For those readers who like lots of detail, we’ve put together all of the idle power consumption values for each supply line in the gallery below:
Voltages
The voltage values are very important because they’re used to calculate power consumption by multiplying them with the amount of current. Looking at the 12 V rail, we see very clearly that the voltage fluctuates extremely if measured in small increments of time. The average voltage is 12 V, but the switched-mode power supply architecture and the different phases of capacitor load leave a very distinct mark. We’d like to tease our reference article about current graphics cards in relation to common power supply units here, which will cover how the two interact in detail. This is a much more interesting topic than it might appear to be at first glance.
We don’t know yet if the high idle power draw represents a problem in our specific board partner’s card or if it’s a problem inherent in the Tonga architecture. Comparing reviews proves difficult once again in light of the scarcity of actual homogenous reference cards. This is too bad, since we’d have liked the Radeon R9 285 to provide a stronger showing in this arena.
