So I recently acquired a power meter and thought it'd be interesting to see how much power my PC setup uses. I then decided to see what effect EIST, C1E and C-States had in typical usage scenarios. Since the scenarios are quite specific, they probably won't be of any use for most people but I decided to post them anyway.
Tests:
Although power usage under load is unaffected, it seems that having all power saving features enabled saves ~25 W not only when idle but in normal usage as well. This is probably the most important thing the results show because obviously this is the state my PC is in most of the time. 25 W may not be much but every little helps.
Like I say, this doesn't directly translate to anyone else's machines but some might find it interesting or useful.
Tests:
- Idle = logged off, monitor off.
- Normal Usage = tray apps, Explorer, 720p video in MPC-HC, VirtualBox, JDownloader, WLM, Firefox (13 tabs).
- Load = same as normal usage plus x264 encode using Handbrake.
- The test wasn't amazingly scientific but I tried to average the results over a ~1 minute period. Results are within 5 W for "normal usage" and "load" and within 1 W for "idle" (since there was far less fluctuation in the reading in this case).
- "Idle" results includes PC and router, "load" and "normal usage" results include PC, monitor and router. My monitor uses ~45 W and my router uses either 12 W or 24 W (can't remember). None of them include my speakers due to plug issues.
- There's no tests for just C1E or C-states because I couldn't find a way to properly disable SpeedStep without also disabling both C1E and C-states (simply disabling EIST and setting the CPU multiplier to 21 manually didn't stop the multiplier changing and neither did setting the minimum CPU multiplier in Windows to 100%). This might be a limitation of my motherboard, I'm not sure.
Although power usage under load is unaffected, it seems that having all power saving features enabled saves ~25 W not only when idle but in normal usage as well. This is probably the most important thing the results show because obviously this is the state my PC is in most of the time. 25 W may not be much but every little helps.
Like I say, this doesn't directly translate to anyone else's machines but some might find it interesting or useful.