The Best Server CPUs part 2: the Intel "Nehalem" Xeon X5570

Power Consumption

The method we used does not allow us to determine the absolute idle power numbers very accurately, but it seems that Xeon X5570 consumes 8W to 10W less when running at idle. Again, all these numbers have a pretty high margin of error, but they are accurate enough to say that the Opteron 2384 consumes quite a bit less at full load while the latest Xeon is clearly the winner when you are running idle. If your application is running close to idle most of the time, with a few spikes at some parts of the day, the Xeon is the performance/watt champion.

The only question is what happens if the server is running most of the time at relatively high load (for example thanks to virtualization)? Then we have to remember that the CPU is only part of a complete server. Let us assume that the Nehalem server consumes 320W (which is close to what we measured). A similar AMD Opteron server can then save about 18W per CPU, and 1W per DIMM as high speed DDR3 is a bit more power hungry than DDR2 (which runs at a lower speed). We assume that we use six DIMMs per CPU.

We could say that the Nehalem is winning by a margin of about 40%. Now, it is clear that the absolute winner is difficult to determine; it all depends on your applications. Still, it is clear that when you compare the best Intel and AMD CPUs, the best performance/Watt figures come from Intel by pretty large margin.