We don’t have a chart showing the idle power consumption of the AMD Phenom II X4 955 because idle power doesn’t change on AMD processors. Once Cool’n’Quiet is active, it will always set the processor to 800 MHz core clock speed and 0.96 V in the case of our MSI 790FX-GD70 motherboard. Hence, the system always required the same 99 W idle power.
The chart shows the system idle power on the Core 2 Extreme QX9650 system at all the voltage levels we tried. The 87 W system idle power could be reached at a voltage of less than 1.008 V, while the 1.192 V default resulted in 94 W idle power.
The power savings through undervolting are significant in the case of AMD’s flagship processor. We started at the default voltage of 1.32 V, which caused a 216 W system peak power, and we finished at only 1.175 V and 179 W peak power. The power savings of 17.2% or 37 W are sufficient to run an additional 20” display within the level of power consumption this system shows today!
Can the Intel system beat the 17.2% reduction in peak power? It can: the quest for the lowest reliable processor operating voltage here resulted in 1.078 V instead of 1.255 V, and a system-wide power consumption of 148 W instead of 185 W—that’s a 20% reduction.