• The FPU unit can be turned off when not needed
• Clock gating is implemented much better
• Each core can run at its own frequency (but the voltage is the highest needed by either core)
• Power for the core and memory controller are split

We measured power consumption using two identically configured Colfax systems running Windows 2003 SP1 64-bit. The server configuration is listed below:

At idle, the Opteron 2350 platform uses significantly less power than the Xeon setup, a decrease of about 44%. While Intel will be able to drop its power consumption with the move to 45nm, the impact won't be great enough to close this gap. The problem here is that Intel must use FB-DIMMs which consume significantly more power than AMD's registered DDR2, short of switching memory technologies there's nothing Intel can do.

Under load, the two are closer in power consumption with the Xeon only using 16% more total system power. Looking at performance per watt, Intel is actually ahead thanks to superior performance under the Cinebench R10 benchmark.