Power consumption with blank screen

Hello *,

I have installed a new PC system

  • OpenSuSE 11.3, 64bit
  • AMD Phenomen II X4
  • ASUS M4A88TD-V Evo/USB3
  • 3 hard disks
  • etc.

After start-up with runlevel 3, no applications running, network is up, the overall power consumption of the PC (without monitor) is ca. 70 Watt.

After some minutes the monitor goes to power saving (terminal mode, runlevel 3 !), but the power consumption rises to 120 Watt! :frowning:

After pressing a key on the keyboard (e.g. Num) the monitor leaves the power save mode, shows the login screen, and the power consumption falls to 70 Watt. :slight_smile:

In parallel I have investigated the system via ssh and running top, but I have not observed any abnormal operation. I looked into /proc/acpi/* but I did not find something unusual.

Any hint why the system needs 50 Watt more with blank screen? What can I investigate?

Thanks in advance and kind regards

Congrats on actually following up on power consumption when most of us don’t!

On general principles, the display and hard drives by far consume more power than any other part of a system. Check if your disk lights indicate activity, I assume that your power saving settings may be set to do a number of things when changing mode like write memory to disk, activate screensaver (BTW - OpenGL screensavers can be processor intensive), more.

Keep monitoring, maybe your power consumption readings will change again after… maybe 5 minutes.


Hi Tony,

thank you for your response!

The system is running on runlevel 3: No graphical user interface running, no screensaver. The CPU load is around 0% (null). There is no disk access, no cronjob, no find,… nothing. Actual I am using the built in graphic interface (on the mainboard), I will install a separate graphic card and try it again.

Thanks - Sven
P.S.: The illumination of a Logitech illuminated keyboard consumes 1 Watt - keep it dark to save money :-))

Even if you’re running in runlevel 3, I can imagine changing modes(eg sleep, hibernation, standby, etc) might still have unpredictable results for several minutes.

Do you have APCI settings enabled (or disabled) in your BIOS/EFI?

Monitors today are getting “smart” in their own right and sometimes do some processing, maybe plug your monitor and system into different sources, then measure each individually. when I refer to “screensaver” I really mean more generically changing the video display, not specifically a GUI Desktop screensaver… Just because a display is blank does not necessarily mean it’s using less power… Blanking a screen mainly avoids pixel burnout (although today’s displays are usually highly resistant to pixel burnout).

As for disks, it may not be enough to simply see no activity, the disks will still be powered and spinning until something powers them down. Activity only means that the disks are definitely not powered down.

Also, I imagine that unless your machine is explicitly put into a resting mode, plenty could still be going on… So, for example consider a NIC… If it’s connected to an active network there could be plenty of continuous networking activity like ARP going on, and if not connected (eg a WiFi NIC) could be trying extra hard to find a connect to connect to.

Whether networking activity would account for 50w, I doubt it (I still suspect primarily the disks)… but maybe something else that’s similar could be happening in your situation.


OK, I think we need more information:

So, am I correct in thinking that you have a hardware power meter (something like a kill-a-watt) in the connection to the system unit and the monitor gets its power via a completely separate connection to the mains? And what technology is the monitor (CRT or LCD)?

After some minutes the monitor goes to power saving (terminal mode, runlevel 3 !), but the power consumption rises to 120 Watt! :frowning:

So, that is the power consumption of the system unit, and not the monitor, or have I misunderstood? Any idea what the processor clock speed does at this time? Is there any sign of sudden disk activity (disk access lights)?

Hallo *,

I think I have to double-check the measurement and to use a second power meter, because the current consumption does not match to the power consumption. :frowning: Maybe there is a problem with the phase displacement, UPS and the power meter.

Yes, I have measured the 225 Volt line before the AC/DC power supply, the PC only, monitor separat connected.

Thank all for the support, I will keep you informed next week.