new iMac Fan speed

Discussion in 'iMac' started by myname70, May 12, 2014.

  1. myname70 macrumors 6502a

    Joined:
    May 5, 2014
    #1
    Guys, I just received my new iMac 21.5" i7 3.1GHz CPU Fusion drive, 16GB RAM. And mentioned the Fan speed is always around 1400 rpm (1396 - 1402). Does not matter if I am in idle (no apps running at all) or video conversion. Eveen the CPU temp is 22 degrees C, the fan speed is still 1400. And see the air flow is going out of the back all the time. Is it the lowest fan speed in iMac? Or I have some issue with the fan control? I use iStat to monitor the speed.:rolleyes:
     
  2. yjchua95 macrumors 604

    Joined:
    Apr 23, 2011
    Location:
    GVA, KUL, MEL (current), ZQN
    #2
    1400rpm is the standard idle speed for 21.5" iMacs (I have a 3.1 i7/16/256/750M model), and even when under heavy loads, it stays silent. The only time I hear it rev up is when doing the Cinebench R15 benchmark or stress-testing it with a utility called Macoh.

    So it's pretty normal.
     
  3. MartinAppleGuy macrumors 68020

    MartinAppleGuy

    Joined:
    Sep 27, 2013
    #3
    Yip. That is normal. My 21" late 2013 iMac has air blowing out the back very silently (I'm in a dead silent room). I never hear it rev up even when doing some gaming (although the air gets a little hotter).

    ----------

    PS- I don't know for a fact, but I think the reasson that the Late 2012 onwards run at 1400RPM minimum and the Late 2011 and before run at 1200RPM idle is due to the fact that the late 2012 and late 2013 have just one fan, where as the thinker iMacs have 2.

    ----------

    What is the minimum speed of the 27" slim's?
     
  4. yjchua95 macrumors 604

    Joined:
    Apr 23, 2011
    Location:
    GVA, KUL, MEL (current), ZQN
    #4
    Not sure, I didn't get around to installing smcfancontrol on my 27" Haswell :p
     
  5. MartinAppleGuy macrumors 68020

    MartinAppleGuy

    Joined:
    Sep 27, 2013
    #5
    Ok :) Let me know if you do.
     
  6. joe-h2o macrumors 6502a

    Joined:
    Jun 24, 2012
    #6
    The Late 2012 slim iMac idles at 1200 RPM in virtual silence, so it has nothing to do with the number of fans in the machine, since the Late 2012 has a single fan.

    The thermal design was carefully tuned by Apple to ensure a machine that would idle silently. The fan choice (not all computer fans are created equal) is all part of that.
     
  7. MartinAppleGuy macrumors 68020

    MartinAppleGuy

    Joined:
    Sep 27, 2013
    #7
    So why do all 21" late 2013 iMacs run at 1400?
     
  8. joe-h2o macrumors 6502a

    Joined:
    Jun 24, 2012
    #8
    Because they're not Late 2012 27" with the 680MX. (I forgot to specify which particular late 2012 I was talking about).

    The thermal profiles are set during design and are known to the fan controller. If 1400 RPM is the minimum speed for the 21" then that's simply the way it was designed. Given that it does not fluctuate more than a few percent outside of this range, and that it's a nice round number, it's clearly the lower ceiling on the controller. It is likely the sweet spot between cooling, noise and ramping up for that particular combination of chassis and fan assembly, just as 1200 is for the 27".
     
  9. MartinAppleGuy macrumors 68020

    MartinAppleGuy

    Joined:
    Sep 27, 2013
    #9
    Here is part of Anandtechs review of the 21" iMac Late 2013:

    "The iMac’s lone internal fan hummed along at ~1400 RPM during light use as well as during repeated Cinebench R15 runs while writing this review."
     

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