Asus P5E3 Premium: A Mean, Green Motherboard?

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TESTING

Test Setup:

Measurement and Analysis Tools


Test setup.

The components chosen for testing where selected to reflect a typical, high-end gaming set-up. Except for the CPU and heatsink, they were the highest performing parts we had on hand. The E7200 processor was not our first choice, but unfortunately it was the first CPU we tested on the board that actually worked properly. A QX9650 and E6750 were tried as well, but for some odd reason, the board automatically overclocked both processors to 450Mhz FSB and increased the CPU voltage, resulting in SpeedStep being disabled and preventing us from testing the EPU feature, which does not function in an overclocked state. We attempted to get around it by setting the CPU speed manually and updated the BIOS, but neither workaround resulted in any kind of resolution.

EPU


EasyTune overclocking.

The EPU feature requires a driver as well as the installation of Asus' AI Gear3+ application. There are five different modes to choose from: Max. Power Saving, Medium Power Saving, High Performance, Turbo, and Auto. Each setting is represented visually by different modes of transport, with the man walking being the slowest and the rocket being the fastest. There is also an Automatic mode (the wand) that scans the system to determine the most optimal overclocking settings. When we tried it, it concluded that the same settings as Medium were appropriate. For testing, we tried each mode and measured the system power consumption at idle, during playback fo a VC-1 clip, and during load.

EPU Setting
CPU Manipulation
System Power (AC)
Mult.
FSB
Clock Speed
CPU Voltage
Idle
VC-1
Load
Max. Power Saving
6.0
241Mhz
1.44Ghz
0.976V
76.9W
88.3W
88.2W
Med. Power Saving
6.0/9.5
253Mhz
1.52Ghz/
2.40Ghz
1.032V/
1.080V
80.9W
87.9W
104.1W
High Performance
6.0/9.5
267Mhz
1.60Ghz/
2.53Ghz
1.128V/
1.176V
81.8W
89.5W
110.1W
Turbo Performance
6.0/9.5
281Mhz
1.68Ghz/
2.66Ghz
1.120V/
1.168V
82.2W
88.9W
111.6W
CPU voltage reported by CPU-Z.

How well EPU performs unfortunately is fogged by the fact that the CPU clock speed and voltage are also altered. Whether the manipulation of the CPU's power phases or simple underclocking and undervolting are resulting in energy savings is hard to tell. Both the idle and load CPU voltage are changed at each level, effectively altering SpeedStep to suit the clock speed EPU has set. The changes are rather moderate, with a slight underclock in effect when using the Medium mode and small overclock using Turbo. Max. Power Saving is the most drastic, severely underclocked the CPU to 1.44Ghz (more than 40%) regardless of CPU load. It's fairly easy to reap significant power savings when performance is crippled.

State
System Power Consumption (AC)
Idle
H.264
VC-1
Load
EPU - High Performance
81.8W
88.4W
89.5W
110.1W
EPU Disabled - Stock EIST
81.9W
88.8W
90.0W
110.2W
CPU speed: 1.60Ghz idle, 2.53Ghz load
CPU voltage: 1.128V idle, 1.176V load

So is EPU actually doing anything? After we uninstalled the EPU driver and AI Gear and rebooted the system, a quick check with CPU-Z confirmed that the stock settings with EIST enabled were identical to the High Performance EPU profile. A comparison of the power consumption between the two states showed very little difference. Our power analyzer rounds off to the nearest tenth of a watt — if it didn't we might not have any results at all. The power savings were so minimal that they're hardly worth mentioning. It's quite possible that EPU just didn't work properly on our test sample, as it did give us trouble early on when we were selecting a CPU to use with it. Another possibility is the E7200 processor we ended up using is not power hungry enough for EPU to make any real difference.



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