Power Consumption and Performance per Watt
What about power consumption?
Idle power consumption remains basically unchanged though the load power consumption is quite a bit lower on the new i7-3820 than on the 6-core SNB-E offerings. Obviously the smaller die, fewer transistors and less cache are making a pretty big difference though the i7-2600K based on the original Sandy Bridge is still lower by 17 watts. Having two fewer memory channels, fewer PCIe lanes and less cache can account for that.
The power efficiency of the Core i7-2600K is actually better than that of the Core i7-3820 in most of our results here thanks to very similar levels of performance and that 17 watt / 10% load power advantage. Compared to the i7-3930K, the new 3820 trades efficiency wins back and forth depending on the application leaving us with no clear winner.