We performed our power consumption measurements using 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 in the PSU itself. In the idle mode we start the system up and wait until it stops accessing the hard disk. Then we use LinX to load the CPU. For a more illustrative picture there are graphs that show how the computer power consumption grows up depending on the number of active execution threads in LinX (both at the default and overclocked system settings).
Because of compatibility issues we uncovered in Gigabyte GA-Z77X-UP4 TH and Gigabyte GA-Z77X-UP5 TH mainboards with our original CoolerMaster RealPower M850 power supply unit, we had to replace it with Enermax NAXN ENM850EW. Both these PSUs have very similar technical characteristics, but Enermax NAXN ENM850EWT is about 1-3 W more energy-efficient than the Cooler Master unit. In order to be able to use the previously obtained results, we decided to make up for this efficiency difference by adding 2 W to all new power readings, so that we could still compare their results against the power consumption of all previously tested products.
We subconsciously expected ASRock Z77 OC Formula to consume more power than other mainboard models in this review. I am sure you will agree that energy-efficiency is not the primary criterion to consider when designing a mainboard for overclocking and setting records. However, our tests showed that under heavy load the board’s power consumption was at an average level and only in idle mode the board consumed a little more than we had expected. Again, it is important to take into account that we disabled “Power Saving Mode” parameter that lowers the Vcore by 0.1 V to ensure a fair comparison. In any case, enabling this parameter didn’t really affect the mainboard’s power consumption in idle mode, but under load it will be even more energy-efficient in this case.
Things do not really change during overclocking. The power consumption of ASRock Z77 OC Formula mainboard in idle mode is above average, and under heavy operational load – on par with other testing participants. Of course, you shouldn’t forget that this board overclocked our test CPU to its absolute maximum, therefore, its power consumption simply can’t be as low as that of the mainboards that didn’t achieve the same overclocking success.