We perform our power consumption measurements with an Extech Power Analyzer 380803. This device is connected before the PSU and measures the power draw of the entire system (without the monitor), including the power loss that occurs on the PSU itself. In the idle mode we start the computer up and wait until it stops accessing the system drive. The mainboards are sorted in the order of ascending power consumption.
The mainboards are comparable in their power requirements in idle mode, yet the Gigabyte is a little more economical.
When we run a processor-intensive application or have a complex x86/graphics load (as in a 3D game), the gap grows larger, yet this is no feat of Gigabyte. The fact is the Gigabyte doesn't increase its processor clock rate much via the Core Performance Boost technology but often drops that clock rate. The ASUS was always faster in our performance tests at default settings, so the lower power consumption comes at the expense of performance. And the Socket FM2+ platform doesn’t have too much performance to start with.
Now let’s see how much power our configurations need with their CPU, integrated graphics core and memory overclocked. The diagram shows the negative effect of the ASUS mainboard's inability to drop the clock rate and voltage of the graphics core in idle mode. The Gigabyte’s power consumption is but slightly higher compared to its results at the default settings. The difference is larger with the ASUS. As a consequence, the gap between the two mainboards is larger, too.
The Gigabyte remains more economical when running applications but it's hard to tell why. The Gigabyte may be slightly more economical to start with and the ASUS wastes a few watts due to disabling graphics-related power-saving features at overclocking. But we guess the difference is mainly due to the fact that the Gigabyte drops its processor clock rate to the default level and even lower, reducing the voltage, too. It is slower than the ASUS as the consequence, so the Gigabyte's lower power draw comes at a cost.
The Socket FM2+ configurations don’t have good power consumption results when overclocked. Thief is a recently released game so we didn’t use it in our tests earlier but you can use the Fritz Chess Benchmark results to compare their power draw with that of LGA1150 platforms. Despite the discrete graphics card, their power consumption is comparable but the Intel Core i5-4670K overclocked to 4.5 GHz is almost twice as fast as its opponent!