We performed our power consumption measurements in nominal and overclocked modes using 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 in the PSU itself. In the idle mode we start the system up and wait until it stops accessing the hard disk. The results on the diagrams are sorted out in ascending order.
The mainboards hardly differ in this test, but we should note that, for all their downsides, the Haswell series should be given credit for requiring less power in idle mode in comparison with their LGA1155 counterparts. Unfortunately, we can’t see that when the mainboards from both manufacturers work at their default settings, so we have an additional test mode called Eco. It means the same default settings but we manually switch all options referring to Intel’s power-saving technologies from Auto to Enabled in the mainboards’ BIOSes. This helped improve the results, lowering the power consumption of the systems to below 40 watts.
We want to remind you that we install an AMD Radeon HD 7970 graphics card into our test configurations. If we instead used the CPU-integrated graphics core, the overall power draw would be lower than 30 watts. Haswell CPUs are indeed very economical when idle, so it is a shame that the mainboards do not ensure this advantage by default. You have to correct some BIOS options for that.
The high load on the Haswell CPU is created by the LinX utility with support for AVX instructions. It is heavier on the CPU than ordinary applications, yet it is just an application nonetheless. It is quite possible that there are some other programs that can be just as heavy. That’s why we stick to using LinX for the purpose of checking the computer out for stability and when measuring its power consumption.
The numbers are high, but they are close to the highest power consumption possible at all. To measure the power draw of our configurations in typical applications, we used the Fritz benchmark. It doesn’t really matter which exactly application you use for that purpose. Any ordinary program that can run on all four CPU cores will produce the same or comparable results. So it turns out that we shouldn’t worry about the high power draw under the AVX-using LinX. The typical power consumption is actually lower than 100 watts. We are only a little surprised to find the Gigabyte GA-Z87X-D3H somewhat more economical than the smaller and simpler ASUS Z87-K.
The mainboards don’t differ much in idle mode even when overclocked.
We don’t have a special Eco mode here because we always use as many power-saving technologies as possible while overclocking. The results are paradoxical even. The overclocked systems (working at increased CPU voltage) need only 38-39 watts, which is comparable to the Eco mode and lower than at the default settings (44-45 watts). It just proves once again how important it is to enable all power-saving technologies if you want your computer to be energy efficient.
The overclocked systems need much more power at high loads compared to themselves at the default settings. The high frequencies and increased voltages show up then.
The ASUS mainboard turns out to be more economical when overclocked, and it’s hard to tell why. The Gigabyte GA-Z87X-D3H has a more advanced power system, which may need more power at high loads, although ensures more stability. The power components on the ASUS Z87-K would heat up to 50°C even at the default settings. In the overclocked mode their temperature was a scorching 70-80°C. We had thought that to be the consequence of the transition of the voltage regulator into the Haswell core, but it is just a downside of the ASUS Z87-K because the same heatsinks on the Gigabyte GA-Z87X-D3H are always barely warm at about 40°C.