New server power consumption

Power consumption of various computers, as measured with the handy Kill-o-Watt
  • 2012 Linux server. 50W – 120W
  • 2011 iMac. 50W – 210W
  • 2010 Windows PC. 120W (always!)
  • 2003 Linux server. 50W

I like how the iMac numbers line up. The iMac has a GPU and a large LCD, so it maxes out higher, but when idle it’s about the same as the Linux server. It’s a very similar motherboard and the same CPU, so that all makes sense.

I don’t quite understand why the idle Linux box is using 50W and not, say, 10W. I don’t think the Intel CPUs will completely shut down a core when idle, that’s part of it.

Update: some useful notes from Intel and on SuperUser. Taking cpus offline via /sys/devices/system/cpu/cpu3/online didn’t save me any power. Either idle CPUs take very little power (unlikely) or the comment on SuperUser is right that this doesn’t halt the processor. The /sys/devices/system/cpu/sched_smt_power_savings also didn’t save me any power. I think sched_mc_power_savings would be useful, but it’s missing on my system. Apparently I need to rebuild the kernel with my processor family to enable it.

Update2: according to this article at low power an i7-2600 uses about 5W. Their measured idle system power (whole computer) is about 70W, so my 50W is in line. Where does it all go?!

At $0.33276/Kwh, every extra watt costs me $0.25 a month.