We pulled some fairly interesting results in measuring power consumption. First, it’s worth noting that with our Core i7 965 engineering sample keyed in to replicate the performance of a Core i7 920, SpeedStep was unavailable, locking clock speed in at 2.66 GHz on our Asus P6T reference motherboard. Thus, all of our idle numbers were measured with each platform running at its rated maximum clock. Fortunately, there’s a new retail Core i7 920 (with its unlocked memory multipliers) en route to the lab right now.
That might help explain the wonky idle numbers, which show the X3 720 sucking down more juice than either of the quad-core Phenom IIs, but it can’t account for the load results. Again, the Phenom II X3 is just way above the other two Phenom IIs.
It’s also worth mentioning that the Core 2 Quad Q9550 is so far down there because that chip is really a Core 2 Quad Q9550S—Intel’s energy-efficient model rated at a 65W TDP (and explored in my more depth right here). It’s really the low-power champion here, even if it costs a startling $400 to the Q9550’s $270.
At the end of the day, it’s AMD’s relatively new 45nm manufacturing process that enables the new Phenom II X4 955 to almost exactly match the X4 940—chalk that 1W difference up to the benefits of running 1.8V DDR3 rather than our 2.1V DDR2 modules.