CPU temperature conundrum

Discussion in 'Mac Pro' started by pertusis1, Feb 5, 2015.

  1. pertusis1 macrumors 6502

    Joined:
    Jul 25, 2010
    Location:
    Texas
    #1
    (If this subject has been adequately addressed in another thread, please feel free to redirect me, but a few searches didn't turn anything up).

    I am stumped. Over the last 2 years, I have had all kinds of fun slowly upgrading my MP 5,1 dual 2.4. My most recent project was to install x5690 CPUs. I used a guide available in these forums, and everything seemed to go smoothly. You might say 'the south wind blew softly.'

    I had some concerns about the temperature of the chips, since the TDP is a bit higher than on the stock chips. I tried to use smc fan control, but couldn't see that it gave me individual CPU temperatures. I installed TG Pro, and when I first booted the computer, while idling, CPU Core B was 71 C, and CPU Heatsink B was 35 C. CPU Core and Heatsink A were close in temperature at about 51 C. I was afraid that I didn't make a good thermal connection with CPU B. Unfortunately, I couldn't find out online which CPU was A and which was B, so I re-silvered them both. The second time I seated the Heatsinks, I think I did a bit better job.

    At any rate, here's my problem. I am rendering a FCPX video and using Civilization V simultaneously. This manages to use about 35% of the CPU load. Here are my current temperatures:

    CPU A Diode 76
    CPU B Diode 61
    CPU Core A 17
    CPU Core B 34
    CPU Heatsink A 64
    CPU Heatsink B 52

    For one thing, it's about 22 C in the room I'm working in, so it seems odd that CPU Core A is 18C. Furthermore, it seems unlikely that the CPU is cooler than the heatsink.

    Does anyone have any suggestions as to how I could sort this out? I feel like I should have good numbers given that I just performed a non-standard upgrade, and am concerned that the sensor data may not be any good.

    Thanks for any help.
     
  2. h9826790 macrumors 604

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #2
    They simply use the wrong terms. That's not CPU core temperature, but "CPU core to processor hot state" temperature. That means, the higher the better.

    The CPU Diode temperature is what you are actually looking for.

    When you test it, you will realise at idle, CPU Diode and CPU Heatsink temperatures are low, but the CPU core is high.

    When loaded, CPU Diode and CPU heatsink increase, but CPU core decrease. And CPU Diode + CPU core always equal to around 95C.

    In your case, it means that CPU A is 17C away from processor hot state, which is normal. And most likely if you stress the machine, the fan will spin up and keep that at around 8C.
     
  3. pertusis1 thread starter macrumors 6502

    Joined:
    Jul 25, 2010
    Location:
    Texas
    #3
    You are a gentleman and a scholar. Thanks a million.

    Just for the benefit of anyone else is my situation, how does one identify which CPU is A and which is B?
     
  4. h9826790 macrumors 604

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #4
    The ident is correct in the apps. CPU A is the rear CPU in the processor board, that means it's cooled down by the relatively warm air coming from CPU B, and that's why it shows warmer than CPU B.
     
  5. Machines macrumors 6502

    Machines

    Joined:
    Jan 23, 2015
    Location:
    Fox River Valley , Illinois
    #5
    CPU A is on the right hand side (or towards the rear of the Mac) when the Tray is installed inside the Mac Pro .

    Here is a naked picture of the 2009 dual CPU Tray for your reference .
     

    Attached Files:

  6. Machines macrumors 6502

    Machines

    Joined:
    Jan 23, 2015
    Location:
    Fox River Valley , Illinois
    #6
    You really need to get bresink's hardware monitor to obtain all the proper sensor data .
     
  7. matthewtoney macrumors regular

    matthewtoney

    Joined:
    Aug 17, 2009
    Location:
    Charlotte, NC
    #7
    Don't get me wrong - Bresink's HM is good, but most of the ones out there that read our Mac Pro's show mostly the same now. *all* of them really should have some verbiage on their display about the "ProcHot" or "Core to Hot State" - this is confusing for lots of people. :(

    (and iStat is the worst offender on that one right now - they start marking it in red when that sensor goes too high even though the higher the safer)
     
  8. Machines macrumors 6502

    Machines

    Joined:
    Jan 23, 2015
    Location:
    Fox River Valley , Illinois
    #8
    It confuses me , and I'm in the business . I know exactly what the various thermal sensors are , where they are ,what they mean and their safe ranges . These utilities are not frank about what the readings really are and then someone comes here in a panic because iStat is telling him his Mac is melting !!! HM is the most useful in an ordinary OS X environment .
     
  9. pertusis1 thread starter macrumors 6502

    Joined:
    Jul 25, 2010
    Location:
    Texas
    #9
    Thank you.
     

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