Mac Pro 3,1 CPU hot after swap

Discussion in 'Mac Pro' started by uller6, Aug 3, 2014.

  1. uller6 macrumors regular


    May 14, 2010
    I just upgraded the CPU on my Mac Pro 3,1 from a Q2.8 E5462 to a Q3.2 X5482. I didn't go with dual processors because I wanted faster single thread performance, and the upgrade from single 2.8 to single 3.2 was only $25. However, the Q3.2 I installed seems to be running really hot under load. My old E5462 ran at 40 C idle, 56 C under 100% load on all 4 cores. The new X5482 runs at 42 C idle, and 79 C under 100% load. However, the CPU heatsink temperature stays about 44C during 100% load. The computer doesn't appear to have any issues with throttling, but the high temperatures concern me. AFAIK the TJunction MAX for the X5482 is 85C, so I'm getting awfully close to this. I'm reading the temperatures of the CPU die and heatsink using temperature monitor lite.

    Does this sound like a poor application of thermal compound? I'm using Arctic Silver 5 with the "line" method covering both cores under the heat spreader. The computer has only been through 3 thermal cycles and about 30 hours of use since I replaced the CPU. Do I have to somehow recalibrate the thermal control system after I installed the new CPU? After installation I did reset both the SMC and the PRAM. Or do these CPUs just run really hot?

    My main concern is that while fine now, running this hot will melt the CPU in 6 months. Does anyone have any experience with the E5462 -> X5482 swap that they would like to share?
  2. NOTNlCE macrumors 6502a


    Oct 11, 2013
    DMV Area
    Well, I don't have experience with the CPU swap, but I can tell you that the X5482s run HOT. My main 3,1 runs dual E5462s and using iStat Menus, I'm at about 102 degrees F for the heatsinks without modifying fan speed. The dies read about 140 with the fans kicked up to 1000 rpm, and one of my CPUs hogs amperage.

    Moral of the story - old Xeons run hot. Don't stare at iStats too long. Worst case scenario, your CPU dies and you buy a new one. I know that sounds terrible, but if your system isn't crashing and there's no throttling, the SMC is doing it's job.
  3. uller6 thread starter macrumors regular


    May 14, 2010
    You're right: given that the computer is working fine I shouldn't worry about the temps, especially for the $25 upgrade cost. The computer definitely feels snappier now with the X5482, so I hope it does last a long time. If the new CPU does burn out I'll just reinstall the old E5462.

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