Michael Schuette from Lost Circuits has an article on-line detailing the power and performance characteristics of three energy efficient processors, the Core 2 Duo E6300 and the AMD Athlon 64 X2 3800+ and 4600+. As usual, Lost Circuits does a great job with the technical analysis. For another take on AMD's Energy Efficient processors, take a look at what we had to say right here.
"With the release of the Core2 Duo line of CPU, Intel has made a complete turn-around in their line-up, pushing the new party line of instructions per Watt. At first glance, primarily the lower speed grades are target for energy-efficiency claims for the simple reason that power consumption increases with frequency in a linear fashion. At close-up, the situation is quite a bit different since Intel's Enhanced Speedstep Technology throttles the frequency of the higher grades back to the same base frequency of 100 MHz while simultaneously lowering the supply voltage, thereby mitigating any potential savings of the lower speedgrades under idle conditions."