Mac Pro 2009 Dual Socket processor upgrade (2 CPUs to 1 CPU)

Discussion in 'Mac Pro' started by NightSun, Jun 28, 2011.

  1. NightSun, Jun 28, 2011
    Last edited: Jun 28, 2011

    NightSun macrumors member

    Jun 1, 2011
    The thread title may sound strange, but here comes the explanation and the question regarding which I would need some help.

    I recently purchased a 2.26 8-Core DP Mac Pro 2009, which came brand new. My plan was to exchange the CPUs and get a higher perfomance, but due to the substantially high price of Dual QPI-link CPUs I cannot afford now more than one. So I picked up a 6-Core 3.33 Ghz Westmere CPU (X5680) (along with all other tools needed because of the increased height of the new setup) and wanted to use it in a single configuration by leaving CPU Socket B empty and doing the upgrade with another X5680 later in the future.

    It has been clear for me that Dual Socket boards should boot up fine with only a single CPU, so I did a quick test: I simply removed the stock CPU from Socket B, and left the other one (2.26) intact. After carrying out the removal my Mac Pro booted up fine, but soon after the desktop appeared, fans started to spin up to max speed, causing me quite much of disappointment.

    Then I reinstalled CPU B and realized that if the screws of the heatsink are not tightened completely, the CPU is not recognized and the same phenomenon happens as before: machine boots up with 1 CPU running and fans spinning up after a while. So all this happens either because the female connector of the heatsink is not plugged in or because the row of power regulators are not touched by the slip of thermal pad at the bottom of heatsink.

    So could anybody help me in finding a workaround for this problem to work with only a single CPU for a prolonged period? I don't know if it could be a good idea to reinstall only the heatsink over the empty socket B to avoid such the spinning up of fans, what do you think about it? Also, one might say that a software-based fan control (like SMCFanControl) could solve the problem, but firstly, it is unclear for me whether the socket is really completely shut down and is it safe to leave the power regulators near the empty socket naked without any cooling and second, software is not a complete solution anyway (the whoosh would reemerge any time you would make a reinstall of Mac OS, for example, and neither do i know if it could be discarded when running Windows in bootcamp, which I will occasionally).
  2. mac.tastic macrumors member

    Jun 16, 2011
    Any change of CPU needs a thermal recalibration.
  3. NightSun thread starter macrumors member

    Jun 1, 2011
    It is clear, just as others posted about it upon carrying out a CPU upgrade, that fan speeds would need some slight adjustment afterwards, using a software-based solution. However, you would not expect more heat when simply removing 1 processor, so this problem is not necessarily about temperature control per se, assuming that the empty socket is completely shut down and its power regulators are not in need of any cooling.
  4. combatcolin macrumors 68020


    Oct 24, 2004
    Northants, UK
    Not worth the effort.

    The last Mac's Apple made to be easily CPU Upgradable were the old G4 towers.
  5. NightSun thread starter macrumors member

    Jun 1, 2011
    Dear Combatcolin,

    Worth or not, this is not the question. Several people reportedly carried out an exchange of CPUs on dual socket 2009 Mac Pros, and while this procedure needs some precaution, it can be certainly done and when financially viable it is indeed worth ever since the firmware upgrade hack has been released that lets you put Westmere CPUs into the 2009 daughterboard - allowing a 2* 3.46 Ghz 12-Core setup at max. If I had two X5680 CPUs at my hand, I would proceed with that right away, and in that case there would not be any fan spinning up problems should the heatsinks be installed correctly. The problem comes up with leaving only 1 CPU on the board, regardless if it is the old one or not.
  6. FFder1. macrumors newbie

    Feb 10, 2008
    My plan is similar to yours.
    I have a 2009 Mac Pro with 8x2.26 and i want to install one X5670 now and a second one later ...
    What have I to regard by the (post-)installation?
    How did you solved the IHS or the spinning fan Problem?
    I am grateful for every tip.

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