Control the maximum fan speed?

Discussion in 'Mac Pro' started by FFder1., Sep 3, 2011.

  1. FFder1. macrumors newbie

    Feb 10, 2008
    I´ve upgraded my 2009- 8x2,26 Mac Pro with one X5670. Later i want to install a second X5670, but for now i am satisfied with only one. But now running the MP with one CPU only, the EXHAUST- & INTAKE-Fan are running alway in the maximum configuration (ca. 2800rpm), which is too loudly and even not necessary (the CPU is around 34°C in idle). So i tried to control the it via software (SMCFanControl, iSTat,....), but they all only change the minimum speed, not the maximum.
    Has anyone a solution to this?

    For the MBA there were a solution found:
  2. mulo macrumors 68020


    Aug 22, 2010
    Behind you
  3. nambuccaheadsau macrumors 65816


    Oct 19, 2007
    Nambucca Heads Australia
    Meanwhile whilst awaiting the second processor, ensure that no heat sensors have become unplugged. Easy to do when replacing processors and that will make the fans run at full bore all the time.
  4. goMac macrumors 603

    Apr 15, 2004
    You need to recalibrate the thermal system.

    Limiting the max fan speed is not a wise idea.
  5. FFder1. thread starter macrumors newbie

    Feb 10, 2008
    I have already done a PRAM-Reset, but this doesn´t change anything at all.

    How can i check, if both heatsinks are correctly installed? Is there a software way to see it? (Both heatsinks are installed, but not tightened too strong, because I am worried about breaking the CPU or the heatsink/daughterboard.)

    I agree with you, that limiting the max fan speed is not the best way.
    By my internet research I also read about a thermal recalibration, but how?
    This can only be done by a Apple Store (
  6. Neodym macrumors 68000


    Jul 5, 2002
    The fans are controlled by the SMC, which has to be reset separately.
  7. FFder1. thread starter macrumors newbie

    Feb 10, 2008
    Quite possible, but also the SMC-reset didn´t solved the problem.
    I try to manage it with the Apple Service Diagnostic tools...
  8. Neodym macrumors 68000


    Jul 5, 2002
    Just re-read your original posting. I think your problem originates from the fact that you are only running one CPU in a system designed for a dual-processor configuration. With the second CPU missing, the system does not get temperature information from that missing CPU, thus assuming it's temperature sensor may be defective and accordingly running the fans in emergency mode to prevent overheating.

    I think the fans will be back to normal once you add the missing 2nd CPU...
  9. FFder1. thread starter macrumors newbie

    Feb 10, 2008
    Yes, this absolute correct. But it does not help me :(
  10. Neodym macrumors 68000


    Jul 5, 2002
    You are basically asking for an override of the emergency routines of your MacPro. This is risky, because they're there for a reason.

    What you could do is to ask the programmers of smcFanControl (they probably know best about SMC) or the wizards over at (have been tinkering with EFI already), if it's possible to selectively shut off the reading of the CPU temp sensor from an unused CPU socket.

    Though it might be less hassle to bite the bullet and get another CPU for the empty socket... (or would you put your MP at risk for doing beta-testing in this area? :eek:
  11. DisTriBution macrumors newbie

    Nov 30, 2011
    this thread is a little old but anyone able to answer the OP's original Q would help out a lot, specifically..

    For THOSE WHO KNOW the answer to this question, I aswell would really appreciate knowing:

    1) the terminal line to set max fan speed for each of the MP's 6 fans.

    2) a list of RPM's converted to hex format for the command line (let us say 300 - 1000 going by 100's)

    3) which smc version to run the term commands with?

    Many people may be tempted to suggest different workarounds or the danger of doing this, but let's just try (as hard as it may be for some) to only focus on the specific question above, thanks for any who reply!!
  12. pooprscooper, Aug 19, 2012
    Last edited: Aug 19, 2012

    pooprscooper macrumors regular

    Aug 5, 2008
    I use the smc included in I copied it over to /usr/local/sbin. Everything has to be done as root to modify smc.

    To set the auto maximum fanspeed for a MBP as listed via smc -f use(where X is the hex converted number you desire):
    /usr/local/sbin/smc -k F0Mx -w X  #left fan
    /usr/local/sbin/smc -k F1Mx -w X  #right fan
    ex: smc -k F0Mx -w 4e20 #left fan 5000rpm max
    Save as and chmod +x it.

    F0 = left fan
    F1 = right fan
    Keep going down the list F0,F1,F2,etc for Mac Pro's 6 fans.

    To manually force a static fan speed:
    /usr/local/sbin/smc -k 'FS! ' -w 0003  # manual fan selection
    /usr/local/sbin/smc -k 'F0Tg' -w 60e0  # left 6200 rpm
    /usr/local/sbin/smc -k 'F1Tg' -w 60e0  # right 6200 rpm
    To set it back to auto fan mode use:
    smc -k 'FS! ' -w 0000  #auto fan selection
    Already converted to hex for you here:

    0000 # 0 rpm
    1f40 # 2000
    2ee0 # 3000
    3e80 # 4k
    4650 # 4500
    4e20 # 5k
    60e0 # 6200
    7080 # 7200
    (FanSpeed x 4) converted to hex ex: 3000rpm*4 = 2ee0
    or use(where rpm is desired speed): perl -e 'print sprintf("%X", (4*RPM))'


    To automate these settings, create a user daemon that loads a .sh file with one of the above options and loop it every minute since waking from sleep will reset it. You can use Lingon 2.1.1(free) to create the com.FanControl.custom.plist. that loads your file like this: [​IMG] Then click "expert mode" in the bottom right and add the following:
    Create a root cronjob to run the .sh file every minute by typing crontab -e and pasting in:
    */1 * * * * /usr/local/sbin/
    Save and quit by press ESC > type a semi-colon and the letter x > press enter.
    Then type crontab -l to make sure it's added.

    Attached Files:

  13. DisTriBution macrumors newbie

    Nov 30, 2011
    Hi Pooprscooper!

    Sorry for the.. eehem.. short delay in responding. I was traveling outside the country for last year+ and haven't had much access. This question is still very relevent to me and I'm sure many others so I REALLY appreciate your well detailed response. Kudos!

    And while it's well detailed, most of it is lost on me because I am just not on the level you're on. So would you humor me:

    - Have you tried this on a Mac Pro (not MacBook Pro or Air) and been able to control the maximum (not minimum) fan speeds? If so, has it worked for all the fans?

    - If you have not done the above, wanna give it a try and let us know? IF you're able to do this, then we will be, albeit with a little more help from you:)

    All the best to you, and thanks again.


    p.s... the speed I'd want to set fans to is:

    300 rpm
    400 rpm
    500 rpm
    600 rpm

    What are the hex values for that?

    Again, thanks!
  14. pooprscooper macrumors regular

    Aug 5, 2008
    It should work fine on a Mac Pro, although I don't have one myself to test. Mac Pro has 6 fans where as my MBP has two. Just keep going down the list of F0, F1, F2, F3, etc. for each fan.

    To convert to the right hex, take your desired RPM and times it by 4 then convert from decimal to hex.

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