Power consumption numbers for my 2011 home machine

October 14, 2011

It's been about five years since I did my last set of power consumption numbers for a desktop. Since I now actually have a new machine, that makes it time for a new set of numbers. I've tried to make the measurements as comparable with the old numbers as possible, but it's not quite an exact match.

The new machine has a CPU with a nominal 95 watt TDP and an efficient 650 watt power supply (vast overkill, but it came with the case). I don't think there's any particularly power hungry components apart from that, especially as I don't think I managed to stress the graphics card at all.

Watt readings taken from our (consumer) power meter, as in the past:

powered off 0 watts
in the BIOS's hardware monitor screen 76 watts
running memtest86+ 86 watts
idle in Linux, with or without the screen blanked 54 watts
streaming writes to one disk 62-66 watts
streaming writes to two disks 73 watts
one core busy with a simple CPU soaker 88 watts (+34 watts from idle)
   two cores busy 107 watts (+19 watts)
   three cores busy 130 watts (+23 watts)
   all four cores busy 154 watts (+24 watts)
four cores busy plus streaming writes to both disks 160 watts
four cores busy with a CPU soaker plus an OpenGL program (glglobe) doing things 151 watts

(I tested the power draw when the machine was powered off because the old machine drew three watts at that point. And it's not a difference between power meters; I'm actually using the same power meter I used five years ago.)

The glglobe test was my attempt to find an OpenGL program that would actually make the machine's graphics card actually do anything meaningful (and thus draw as much power as it could, since I've seen this make a clear difference). I suspect that the program wasn't making the card work very hard, plus there is the oddity that the power draw actually dropped compared to the four CPU soakers alone. (And yes, this wasn't a measurement artifact; when I quit glglobe, the power draw immediately jumped up.)

All of this was under Fedora 15 with Gnome 3. I didn't attempt to optimize or change any power profiles from the default setup.

Overall I'm happy to see that under full load the new machine draws no more power than the old machine, and it idles at significantly less power than the old one did (54 watts versus 98 watts). Since I last did this check in an era when machines were drawing more and more power every generation and every year, it's a pleasant change.

(Admittedly I think that five years ago may have been the tail end of that era, when everything started slowing down and people began to care about issues like machine noise.)

PS: if you know a better OpenGL stress test that's packaged for Fedora, let me know.


Comments on this page:

From 131.137.219.14 at 2011-10-14 10:41:48:

does fedora have glmark2?

No idea how much stress it puts on the gpu. It does peg one of my cpu cores which may not be a good sign. Using the radeon opensource driver with a "ATI Technologies Inc RV370 [FirePro V5700]"

By cks at 2011-10-14 11:35:44:

Unfortunately, glmark2 isn't packaged for Fedora and when I took a stab at building and running it by hand it exploded messily (with core dumps).

Written on 14 October 2011.
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Last modified: Fri Oct 14 01:14:55 2011
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