Power Consumption: A Detailed Look At Idle
ZeroCore Power is an interesting feature that represents the best solution for minimizing idle power draw in dual-GPU systems. At least in theory, the graphics card that isn’t needed can simply be turned off. PowerColor tries to illustrate the concept on the back of its Devil 13 board using two LED panels indicating each GPU's consumption.
Clearly, PowerColor put a lot of emphasis on its power handling, so we were fairly surprised by our measurements. At 36 W during idle, that's higher than we'd expect, especially considering that AMD's Radeon R9 295X2 idles more than 10 W less without ZeroCore Power. Once the 295X2 partially shuts down, it drops under 14 W (which is less than half of PowerColor’s result).
These numbers were repeated several times and the outcome is consistent: PowerColor's power supply is definitely different from AMD’s. Let’s first compare the Devil 13 Dual Core to the Radeon R9 295X2.
The first eye-opening result is that the Devil 13 draws 14.8 W from the motherboard slot alone, which is already more than AMD's dual-GPU Radeon when one of its GPUs is disabled.
Since this portion of the power draw is independent of ZeroCore, it results in an extremely high constant minimum power draw just based on component choice and layout. Conversely, AMD doesn’t use the motherboard's 3.3 V rail at all.
Now we'll compare power consumption at the two pairs of eight-pin auxiliary connectors, each of which corresponds to one GPU. The active processor draws just over 10 W through PCI Express, whereas the turned-off GPU still eats up 8 W. Tack that onto high power use from the motherboard and you end up with use reminiscent of AMD's Radeon HD 6990.