Power And Efficiency
Though we’ve seen overall performance improvement from Intel’s Sandy Bridge architecture, power consumption was the reason we wanted to put this mobile flagship through its paces. Desktop uses might not care as much, but any power savings can pay big returns in battery life and notebook noise.
The Core i7-2920XM appears to save a little energy compared to the Core i7-940XM, but an exact analysis is impossible without getting the older system back for new tests with a newer graphics card. Enough data exists for us to notice that the Core i7-980X (with Nvidia's GeForce GTX 480M) used 69% more idle power and 75% more load power than the i7-940XM, and that that the same-model Core i7-980X (with GeForce GTX 470M graphics) consumed 170% more idle power and 134% more load power than the Core i7-2920XM.
Dividing average performance by average power makes the comparison much easier, because it shows that the graphics card accounts for only a few percent of the overall power-to-performance ratio. The mobile Core i7-940XM saved power by being a lesser performer, while the desktop i7-980X used most of the the extra power it consumed to produce big performance gains. The Core i7-2920XM mixes some top-performance scores with low-power numbers to prove itself more than 50% more-efficient than either its desktop or high-end-mobile predecessors.