Here's how the motherboard stacks up in real life against a couple different motherboards. We have no way of directly measuring motherboard power draw, so PCSTATS measures total system power draw and compares that in CPU-loaded (max value recorded in Prime95) and idle states (at Windows Vista desktop). An Extech 380803 AC Power Analyzer and A-PFC compliant PC Power and Cooling 750W power supply were used for these tests.

System Power Draw Tests: (PCPower 750W PSU) Desktop Idle (W) Watts Ranking Intel DG45ID (Intel G45 200/800 C2D E6750 Onboard G45 ) 68 Asus P5Q-EM (Intel G45 200/800 C2D E6750 GF 8800GTS 320MB) 131 Asus P5Q-EM (Intel G45 200/800 C2D E6750 Onboard G45 ) 72 Foxconn A7DA-S (AMD 790GX 200/800 AM2 X2 5000+ GF 8800GTS 320MB) 131 Foxconn A7DA-S (AMD 790GX 200/800 AM2 X2 5000+ onboard HD 3300 video) 61 Biostar Tpower N750 (NF 750a 200/800 AM2 X2 5000+ GF 8800GTS 320MB) 110 Biostar Tpower N750 (NF 750a 200/800 AM2 X2 5000+ onboard nF 750a video) 45.4 Prime95 Stressed (W) Watts Ranking Intel DG45ID (Intel G45 200/800 C2D E6750 Onboard G45 ) 121 Asus P5Q-EM (Intel G45 200/800 C2D E6750 GF 8800GTS 320MB) 224 Asus P5Q-EM (Intel G45 200/800 C2D E6750 Onboard G45 ) 122 Foxconn A7DA-S (AMD 790GX 200/800 AM2 X2 5000+ GF 8800GTS 320MB) 192 Foxconn A7DA-S (AMD 790GX 200/800 AM2 X2 5000+ onboard HD 3300 video) 121 Biostar Tpower N750 (NF 750a 200/800 AM2 X2 5000+ GF 8800GTS 320MB) 187 Biostar Tpower N750 (NF 750a 200/800 AM2 X2 5000+ onboard nF 750a video) 127 3DM06 IGP Stressed (W): Watts Ranking Intel DG45ID (Intel G45 200/800 C2D E6750 Onboard G45 ) 115 Asus P5Q-EM (Intel G45 200/800 C2D E6750 GF 8800GTS 320MB) 182 Asus P5Q-EM (Intel G45 200/800 C2D E6750 Onboard G45 ) 119 Foxconn A7DA-S (AMD 790GX 200/800 AM2 X2 5000+ GF 8800GTS 320MB) 223 Foxconn A7DA-S (AMD 790GX 200/800 AM2 X2 5000+ onboard HD 3300 video) 124 Biostar Tpower N750 (NF 750a 200/800 AM2 X2 5000+ GF 8800GTS 320MB) 226 Biostar Tpower N750 (NF 750a 200/800 AM2 X2 5000+ onboard nF 750a video) 118

The Asus P5Q-EM's power draw at idle is highest amongst the integrated motherboards tested, although once the system is stressed the power drawn falls into line.

Asus' Energy Processing Unit (EPU) is built into the Asus P5Q-EM motherboard, and what the EPU does is dynamically alter the amount of power phases the motherboard uses depending on usage and system load. PCSTATS tested the EPU along with is accompanying software.

The EPU software isn't quite as helpful or as informative as the Dynamic Energy Saver software found with the Gigabyte EP45-DS4 motherboard. Here we have an option to switch between power saving mode and performance mode, or place the entire Asus P5Q-EM system on auto. The amount of power saved isn't reported back to the user except in the cryptic form of the amount of CO2 emissions reduced, which in turn assumes your computer is powered by coal. Give us actual wattage used! Display wattage savings over time!

This sub-menu is a little more interesting, and can be used to set manual voltage throttling limits on the CPU. This will have a direct impact on system performance, but does save quite a bit of wattage at its most extreme settings (note Asus EPU will throttle CPU clock speed to save power). Unfortunately there's still no direct display of the actual numbers, so it's difficult to know how much of a voltage downgrade "high" is compared to "medium".

Finally, PCSTATS plugged the P5Q-EM in, turned on the EPU, and re-ran our power draw benchmark tests.

Energy Saving - Total System Power Draw Motherboard State: Power Draw: w/h ASUS EPU: Approx. Power Saved: Desktop Idle 72 W 68 W 4 W Prime 95 Stressed 122 W 117 W 5 W IGP 3DMark06 Stressed 119 W 119 W 0 W

The EPU isn't doing a whole lot here to modify the power being consumed by the Asus P5Q-EM motherboard - saving 5 watts at stressed isn't particularly impressive. Turning on the EPU for idle power saving can make for some power savings over a long term period. Over the lifetime of a motherboard's use, shaving off even a few watts overall from a system that's always on can equate to some money saved off the electricity bill.

Okay, on to the highlights of the Asus P5Q-EM motherboard.