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’s power consumption grows up depending on the number of active execution threads in LinX (both at the default and overclocked system settings). We often point out that on many mainboards certain power-saving technologies are disabled by default. Therefore, besides power consumption in nominal mode with all default settings, we also measured the power consumption of test systems with all power-saving technologies (including the proprietary ones) manually enabled.
Unlike many other mainboards, where different power-saving models are disabled by default, we couldn’t complain about the same on Asus P9X79 Deluxe mainboard: all options were enabled and all parameters were set to Auto. However, we have already seen many times before that “Auto” doesn’t necessarily mean “Enabled”. If we manually enable all processor power-saving features and also activate Asus’ own technologies, such as dynamic change of the number of active phases in the voltage regulator circuitry depending on the processor utilization at the given time, we will manage to save a substantial amount of power in all modes, as we can see from the first two diagrams. In other words, the mainboard may in fact be much more energy-efficient than with nominal default settings.
Of course, during overclocking with voltage increase, the system power consumption also starts to grow, but in return we get a significant performance boost compared with the nominal mode. However, you should keep in mind that an overclocked system consumes even a little less than the nominal one in idle mode (104 W vs. 105 W). We increased the processor core voltage and memory voltage, we added an additional fan to cool the components around the processor socket during overclocking, which increases the consumption by another 1.5-2.5 W, but at the same time we enabled all available power-saving features. The result is pretty paradoxical: the overclocked system turned out more energy-efficient in idle mode than the system working with nominal settings. I believe it is hard to come up with a more illustrative example of how important and useful power-saving modes are.