The power consumption of the AMD Phenom II X4 955 was quite good, and the use of DDR3 memory helped shaving a few watts off.
Under full load the Phenom II X4 955 used 5.5% less power than the Core i7 920, and 12% less than the Core 2 Quad Q9650. However, when at idle the Phenom II X4 955 used up to 20% more power than the Core i7 920, and 8% more than the Core 2 Quad Q9650.
Whatever there was to praise about the Phenom II X4 955 efficiency was true when testing the X4 940 and 920 processors, certainly a huge improvements when compared to the older Phenoms but just about on par with what Intel has to offer. Idle consumption could definitely be better on the X4 955.