We measured the power consumption using Extech Power Analyzer 380803 device. This device was connected before the system PSU, i.e. it measured the power consumption of the entire system without the monitor, including the power losses that occur in the PSU itself. When we took the power readings in idle mode, the system was completely idle: there were even no requests sent to the hard drive at that time. We used LinX program to load the Intel Core i7-860 CPU. For more illustrative picture we created a graph showing the power consumption growth depending on the increase in CPU utilization as the number of active computational threads in LinX changed in nominal mode as well as during overclocking.
And here a pleasant surprise awaits us. There is nothing strange about the equal power boards consumption in nominal mode, but also during overclocking the two graphs almost coincide. Yes, we do see that during overclocking, when there is no CPU load Gigabyte GA-P55-UD6 mainboard consumes a little more than Asus P7P55D Deluxe, but the difference is minor: only 7 W. It happens because Asus mainboard keeps all processor power-saving technologies up and running when we change the processor core voltage, while Gigabyte doesn’t know how to do it. However, the CPU doesn’t work, even though it receives higher core voltage. It doesn’t spend any power, so the total system power consumption makes 159 W by Gigabyte versus 152 W by Asus. And under different types of workload both mainboards send about the same voltage to the CPU that is why they again demonstrate the same power consumption.
When we discussed different overclocking methods on Asus P7P55D Deluxe, we compared not only the performance, but also the power consumption with dynamic and static Turbo Boost technology implementation. It turned out that in idle mode the dynamic version is more energy-efficient offering almost 30 W advantage. The thing is that when we enabled C3-C7 states for dynamic implementation in the BIOS, we allow the CPU to go into deeper power-saving modes in case there is no load and thus disable more units. This way, if we compared the boards during overclocking using dynamic Turbo Boost, the power consumption difference between them in idle mode would be way greater and would exceed 30 W. In this case the CPU on Asus board could go into deeper power-saving states, unlike the CPU on Gigabyte board.
The results of our power consumption comparison are quite good for Gigabyte GA-P55-UD6. Despite its obviously disadvantageous position because of non-operational power-saving technologies in case of modified CPU core voltage, it does lose a little, but nevertheless, not as much as we would expect it to.