Sorry - Another Quick CPU Fan Speed Question...

Discussion in 'iMac' started by chilli42, Sep 6, 2011.

  1. chilli42 macrumors newbie

    Feb 1, 2010

    Just got a new 2011 iMac 2.5 GHz Intel Core i5 21 inch. First mac and loving it so far! I can hear the fans just slightly at idle in a quiet room and checked on this forum to see what is the normal idle fan speed.

    Most of the results come back with the CPU fan running at around 938 rpm. mine is constant at 1199 rpm. A few others have this speed too, but he majority are around the 938 rpm level (some much higher). My temps also seem lower than most at idle too (due to the higher fan speed i guess).

    OP Drive 998
    HD Drive 1099
    CPU 1199

    My question/s:

    Why the difference between machine (shouldn't they be set the same in all machines with the same spec with software)?

    And is the normal??

  2. Big-TDI-Guy macrumors 68030


    Jan 11, 2007
    Normal. Some peoples rooms are different temperatures, different display brightness settings, "idle" background processes.

    Then you have variations in the fan speeds due to temp sensors reporting slightly differently. The temp sensors don't have to be calibrated - evident by my iMac reporting ambient as 80F, when using a calibrated thermocouple - it was actually 71F at the same location.

    The thermal management is very good - if you want higher speeds / lower temps - download SMC fan control - but in all truth - it's likely just fine.
  3. sjinsjca macrumors 68020


    Oct 30, 2008
    Many things can affect fan speed. Computer activity, display settings, power management settings, ambient temperature, ventilation, altitude, humidity...

    Don't worry about it. It Just Works.

    [Edit] ...Forgot something. If your machine is brand-new, then Spotlight is busy building its first index. That represents significant activity that you might not even know is going on. There can be many dozens of other details that factor into it, too-- for example, if your rev. of Flash is different from your friends' version, that can make a profound difference. But the advice remains the same: don't worry about it, just enjoy your gorgeous new machine.
  4. chilli42 thread starter macrumors newbie

    Feb 1, 2010

    Will it do any long term damage to the fan? Seems to stay the same regardless of if the room is hot or cold (if I have the air con on or not).

    Is there a standard apple operating speed that I could adjust with fan control or just leave it? Also, would I notice it being quieter with it at 938 compared to 1199?


    A couple of weeks old with little usage time. Thx very much for your comments!
  5. Big-TDI-Guy macrumors 68030


    Jan 11, 2007
    If it's loud enough to bother you - get it checked out.

    There are dozens (or more) temperature sensors inside your iMac, with multiple cooling fans. They all work together to provide the best cooling - while producing minimal noise. Finally, you have hard limits at the hardware level - so if the temps on critical components get too far beyond a safe threshold - your computer will just shut off - OS be damned.

    Increase the speeds by a bit - but I wouldn't slow things down beyond the minimum OSX is currently holding your system to.
  6. chilli42 thread starter macrumors newbie

    Feb 1, 2010
    Thanks for your help. I guess if other people seem to have identical speeds too, then must be okay. Will keep an eye on it.
  7. bpeeps macrumors 68030


    May 6, 2011
    Your Mac is fine. But I'm sure if you want to find something that isn't perfect, you will.

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