The power consumption difference between MSI and ASUS mainboards remains small only if the systems are not overclocked or overclocked just a little bit. Once we overclocked Intel Core 2 Duo E4300 processor from 200MHz to 350MHz FSB without even adjusting the voltage, the situation changed dramatically:

MSI P7N SLI Platinum mainboard sticks to the overclocking settings: 151W in idle mode, 216W in burn mode. However, on ASUS P5N-D “smart” BIOS jumps in. it increases the processor Vcore beyond 1.4V, so that the mainboard starts consuming 161W in idle mode and 234W in burn mode. Even locking the voltage at the nominal 1.325V doesn’t save the situation. Under heavy workload the mainboards run neck and neck in terms of power consumption. However, in idle mode only the frequency multiplier lowers on ASUS board, but not the voltage, so the board again turns out the most power-hungry.

It is hard to estimate the value of ASUS EPU technology. You can notice it working only if you use AI Gear3 utility and the default processor voltage is lowered. But it is a hardware technology and should work automatically, shouldn’t it? In this case, if the savings are so low that we can barely notice them, then the technology is a failure. But maybe it does work and without it ASUS mainboard would be consuming even more power? In this case, the technology is a success. However, in any case, ASUS P5N-D mainboard cannot really boast any “great energy efficiency”. What the users care about most is the outcome, and it shows that ASUS P5N-D mainboard is still the most resource-hungry with or without EPU technology.

So where do the claimed saving rates of 58.6% and even 80.23% come from? Of course, different mainboards will have different power savings, but how did they actually calculate the percentage? The answer to this question is available in ASUS marketing materials. Namely, the number 80.23% is mentioned in a video made for EPU on ASUS P5E3 Premium mainboard. You can even see how they came up with this impressive number:

However, you have to look not at the numbers but at the comments in small gray font. They compared the power consumption of ASUS P5E3 Premium mainboard with that of some other mainboard with disabled Intel power-saving technologies, and this way prove the efficiency of the ASUS EPU. Of course, a mainboard with the CPU clock frequency multiplier and Vcore remaining unchanged all the time will lose to any other board with these technologies activated. And no ASUS EPU is necessary here.

We all understand very well that marketing materials will never get to the root of things, will never study all cons and pros of the promoted solution. Marketing should highlight some features of the product so that it could cover all possible drawbacks and issues. However, in this case they seem to be misleading us deliberately, even though the numbers are indeed correct. According to this marketing promotion, we will buy a mainboard that will be practically as efficient as any other good mainboard on the same chipset. Only if we use additional software we will see the difference, because the core voltage will be reduced below their nominal value and the performance will be lowered in maximum power saving mode. But we will certainly never be talking bout 58.6% or even 80.23% if we compare the boards in fair conditions. And if we overclock our processor, then ASUS mainboard will consume much more power because of the typical issues pointed out above and of the “smart” BIOS. That’s for sure.

The last straw that broke the camel’s back was the power consumption table where we compared mainboards on different chipsets. Let me say a few words about the testing conditions and participants.

All power consumption tests were performed in the same version of Windows Vista OS, only the mainboards on NVIDIA nForce 750i SLI chipset and processors were different. Then I confirmed that ASUS P5N-D mainboard was stable with Intel Core 2 Duo E8400 processor overclocked to 400MHz FSB. But before I started the performance tests I reinstalled the OS, without changing any settings. I installed Service Pack 1, all necessary drivers and applications. The systems were theoretically setup identically, but our tests showed that ASUS P5N-D mainboard consumes 9W less power when tested on a freshly installed Windows Vista SP1 OS.

Of course, system power consumption depends on voltage settings. we have also proven experimentally that it depends on temperatures, too: the higher the temp, the more power is actually consumed. But I have never known that I can save power by simply reinstalling the operating system. Power consumption is not a constant value. It keeps changing all the time, so we can certainly disregard the numbers past decimal point. But you cannot disregard an 8-10W difference. It remained in idle and burn modes, at nominal and overclocked speeds.

abit IP35 Pro mainboard on Intel P35 Express chipset was tested only on the freshly installed OS. ASUS P5N-D was tested on both, just for your reference, although we can only make any conclusions from comparing the results from the same OS version.

Very interesting: at nominal as well as overclocked CPU speeds, the system on Intel P35 Express chipset with 100% CPU utilization by S&M consumes almost as much power as Nvidia nForce 750i SLI based mainboard in idle mode. Even less. So, ASUS P5N-D mainboard cannot be called economical at all, no matter what technologies or features it supports. Simply because it is based on Nvidia nForce 750i SLI.