Originally Posted by posh rat in hell

I don't know that I'd really quantify it that way. If you have a need for >4GB of ram, there is a benefit to using 64 bit processors. Otherwise, I would let performance per watt be the deciding factor. The amount of electricity used by a modern high performance CPU is non-trivial, and all electricity used is ultimately converted to heat, which then requires more electricity for a compressor to move the heat outside and cool your office/datacenter/(bedroom? )

A core duo processor pulls approx 27 watts. A P4 Xeon processor pulls approx 150 watts. The core duo does about twice as much work as the P4 Xeon.

Intel is going to be releasing a new Xeon chip based on the same technology to improve the performance per watt.

I would personaly prefer a bunch of Core Duo's in a datacenter than a bunch of P4 Xeon's, but there doesn't seem to be any servers that use those chips *yet*.