Fan noise after adding RAM...

Discussion in 'Mac Pro' started by yertleturtle, May 29, 2015.

  1. yertleturtle macrumors newbie

    Oct 20, 2014
    I just upgraded my ram on my mac pro 3,1 (2008) and the fan is now running at 2500 RPM even though the temp is only 27 C. Two chips of the old memory (Riser A/Dimm 1 and 2) don't show a serial number. Everything else looks correct to my eyes. Any help is appreciated.

    Included is a screenshot of my System Info.

    Attached Files:

  2. ActionableMango macrumors G3


    Sep 21, 2010
    I'm guessing you bought FB-DIMMs that don't have a temperature sensor. At least one other person has reported the same problem (high fan speeds) for that reason.

    Basically, in order to be quiet, the MP uses just enough fan speed to keep things cool. If there is no temperature sensor, it doesn't know how hot the RAM is, so it runs the fans at maximum and/or slows the RAM down.

    From the 2008 MP manual:
    From Apple (Technical Note 2156):
    I would look up the model number of your memory sticks to see if the specs state whether or not they have a temperature sensor. A lot of RAM sticks, even ECC server RAM, don't have the sensor.

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