Up until this point we’ve established that Intel’s Core i7 920 overclocked to 3.8 GHz is faster than an overclocked Phenom II X4 940 almost across the board. It’s also more expensive, due to its motherboard and DDR3 memory requirement. But where do the two platforms fall with regards to power when overclocked?
At idle, there is no contest. Cool’n’Quiet spins the Phenom II down to about 800 MHz at the Windows Vista Balanced setting. As a result, the entire platforms hovers right around 175 W of power consumption. Enhanced SpeedStep technology isn’t quite as friendly to the Core i7, and we still saw speeds around 1.6 GHz at idle. As a result, the i7 920 build never dropped below 255 W at idle.
Crank up the load, however, and simple math starts working against the Phenom II, as its elevated voltage results in higher power consumption. The gap that existed at idle is gone, and now the 3.64 GHz chip is chewing up 10 more watts than the Core i7 does.
Bear in mind that, most of the time, your system will likely be idling. So overall, the Phenom II is going to be the lower-power solution. However, when the rubber hits the road, it’s just as power-hungry as Intel’s i7, even in light of AMD’s new 45 nm process.