Nehalem manages between 0% and 40% performance increase clock-for-clock compared to penryn. But with a power consumption cost of 10% for the whole system, which is driven by about 20% extra power for the CPU. http://www.anandtech.com/cpuchipsets/intel/showdoc.aspx?i=3326&p=7 So, Nehalem, TODAY, is not impressive at all. You can get the same performance per watt by just overclocking a penryn. However, I'm sure the figures will improve once they optimise mainboard, BIOS, memory channels, and final (non-engineering sample) CPUs will have low power requirements. Or rather, lets hope so, otherwise Nahelem is a flop, and NOTHING like the mammoth win when Intel moved to Core 2 architecture.