Activity Monitor CPU idle percentage wrong

Discussion in 'Mac Pro' started by BobbyJ, Jan 13, 2010.

  1. BobbyJ macrumors newbie

    Jan 13, 2010
    I have a 2.66 quad core 2009 Mac Pro. Running 10.6.2. I see weird behavior in the Activity Monitor. The "% idle" number jumps from 49% to 61% to 99% (but usually stays around 49%), when I'm actually 99% idle. The "% user" and "% system" just don't add up to "% idle." Does anyone else see this? I'm wondering if it has anything to do with the RAM I just installed, or if this is a coincidence.
  2. t_e_c macrumors newbie

    Feb 13, 2010
    CPU idle percentage wrong

    I have the same issue with a new 27" iMac with a 2.8 quad core CPU. The weird thing is that I have already returned two iMacs with the same problem. It seems to run hotter than the iMacs in the store. Did you ever find an answer to the problem? Apple Care has not been any help.
  3. Inconsequential macrumors 68000

    Sep 12, 2007
    Mines the same, but I think its not adding all the CPU tasks, SystemUI uses around 1-10% so I think its that.

    Nothing to worry about tbh.
  4. Mattww macrumors 6502


    Jan 11, 2008
    I have the same symptom on my 2.26Ghz 8-Core - I initially noticed it after the audio update so assumed it was due to this but I checked another Mac Pro that hadn't had the update installed and it had the same issue so it must have happened before - maybe after the 1.4 Firmware update?

    If I give the computer a few minor tasks to do the idle percentages are correct ( for example 98%) - even a web page with a Flash video is usually enough. It seems to only get it wrong when the computer is truly very idle then it shows around 50%. My best guess is that the processors are down clocking to save power and activity monitor doesn't know how to deal with it? If you run something else like iStat Pro it shows the correct percentage.

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