nMP PCIe Switch Diode very hot

Discussion in 'Mac Pro' started by armut, Aug 6, 2015.

  1. armut macrumors member

    Joined:
    Jul 9, 2014
    #1
    Hello people,

    I have a problem with my nMP.
    I recognized via iStat Menus that my PCIe Switch Diode is getting very hot.

    To lower this I did NVRAM- and PRAM-Reset but nothing changed.

    Do you know how to fix this or what the problem is?

    Thanks...
     
  2. h9826790 macrumors G4

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #2
    I don't have a nMP, but post the screen capture may help the others to give out better comment.

    Also, quite a few of these hardware monitoring softwares (including iStat) are not optimised for Mac Pro (both new and old), they may give out useless reading, or use confusing terms which makes you believe that the computer has problem. In fact, in most case, the computer is indeed perfectly normal.
     
  3. armut thread starter macrumors member

    Joined:
    Jul 9, 2014
    #3
    Thank you for your replay.

    Here is the screenshot.
    Now its a little bit lesser than before because the temperature was about 87°.

    I hope you can help me. I also have no Apple Protection Plan.
     

    Attached Files:

  4. h9826790 macrumors G4

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #4
    I think now the others with the nMP may able to help you by comparing the numbers from their machine.

    Anyway, will the temperature drops if you manually set the fan speed to something like 1200RPM?
     
  5. armut thread starter macrumors member

    Joined:
    Jul 9, 2014
    #5
    The temperature is going down to 72° when I set the fan speed to 1900 RPM but I have also to say that we have about 35° outside...
     
  6. DeltaMac macrumors G3

    DeltaMac

    Joined:
    Jul 30, 2003
    Location:
    Delaware
    #6
    That's just one temp (out of many), and not something that should worry you...
    87 C is hot, but not dangerously so.
    Why do you think that's a problem?
    Are you having other troubles with your nMP?
     
  7. armut thread starter macrumors member

    Joined:
    Jul 9, 2014
    #7
    No, I do not have any problems but I recognized it because the PCIe Switch Diode was marked red.
     
  8. h9826790 macrumors G4

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #8
    IStat turn the numbers in red by their own logic, there is no real relationship between red number and abnormal.

    e.g. On cMP, there is a number called "Core X Relative to ProcHot". In fact, this number is the bigger the better, but iStat will turn it into red when it over certain level, which cause some users believe their very good Mac Pro is running hot.
     
  9. armut thread starter macrumors member

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    Jul 9, 2014
  10. AppleDroid macrumors 6502a

    Joined:
    Apr 10, 2011
    Location:
    Illinois
    #10
    Was just going to add my system with d300s also reports much higher Pcie switch temps as well. Seems to be a common thing with stat and these machines.
     
  11. theSeb macrumors 604

    theSeb

    Joined:
    Aug 10, 2010
    Location:
    Poole, England
    #11
    Mine is currently at 73 Celsius with the fan on at the lowest speed. It seems to stay at around that point on my machine, looking at the history in iStat
     
  12. SoyCapitanSoyCapitan macrumors 68040

    SoyCapitanSoyCapitan

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    Location:
    Geneva
    #12
    Ambient temperature. If your room is 20 degrees you should expect that chip to run around 68-75c depending on how much load it is under. For every degree the ambient temperature increases the Mac can't remove the same amount of heat, so it has to get hotter. Reduce the room temperature.
     
  13. filmak macrumors 65816

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  14. Xde, Jun 7, 2018
    Last edited: Jun 29, 2018

    Xde macrumors member

    Xde

    Joined:
    Jul 11, 2016
    #14
    The PCIe switch is a PEX 8723 from Avago/Broadcom.
    This part is not listed on Broadcom, maybe a part for special costumers.
    A similar version is PEX 8724.
    This chip has a metal case and is located on the new Mac Pro i/o board on the outer side, beside the mains connector.
    Picture from „i fix it“: https://d3nevzfk7ii3be.cloudfront.net/igi/XhGBBKpAXc3SZwGp.large

    When a Mac Pro is turned on from cold state, the chip has immediately around 60 degrees celsius.
    After 10 minutes of idling or Safari usage, the temperature increases up to 75 degrees, more or less,
    depending of the room temperature and workload. Can reach easy 85 degrees on some circumstances.

    When I look into the PEX 8724 data sheet,
    power dissipation is 5 watts and the temperature specs are 0 and 70 degrees celsius.

    Related to these specs, this chip seems to be overloaded, with the given data of the temperature apps. All apps are showing same results, I am using MacsFanControl.

    I imagine, if this values are real, Apple should have discovered this and would have used a
    heatsink on the chips metal surface.

    Has anyone some more insight into this temperature thing? I mean some more than "this is okay".
    thanks everyone!
     
  15. hammo123 macrumors member

    hammo123

    Joined:
    Jun 9, 2013
    #15
    Out of interest I checked my PCIe Switch Diode temp using Macs Fan Control, I don't have iStat menus.
    I took screenshots of the temps both loading the CPU and then 5 minutes later at idle.
    Seems to be pretty steady around 63-66C.

    [​IMG]

    [​IMG]
     
  16. Xde macrumors member

    Xde

    Joined:
    Jul 11, 2016
    #16
    Right. But depends on the outside temperature. At 20 degrees your value might stay a while.
    Startup temp is close to 60.
    With 26 degrees outside temp (no aircon), value will climb over 70 degrees easily, nearly at idle.
    Now in summertime, I have 70-75 degrees everyday, only looking some websites.
    Maybe it is not an extreme, but compared to CPU/GPU wich are around 38 degrees, it seems
    high to me. Just when the datasheet says 70 degrees max.
    If I could reach this chip easily, I would have set an heatsink on top.
     
  17. Xde macrumors member

    Xde

    Joined:
    Jul 11, 2016
    #17
    Edit from my post obove...
    I thought, it is needed to highly disassemble the Mac Pro, including the flexcables, to reach the chip.

    Sadly, the chip is deeply inside the Mac Pro.
    But now I imagine, removing only the bottom case part of the Mac Pro could gives access to the chip.
    I am not sure, if the circular logic board needs to be removed, but I imagine, the diameter of the board is smaller,
    so that it may be possible to reach the location.

    There is only little space in the gap between the i/o board and the connectors rear panel.
    Additionally, just aside of the mains connector, there is the mains cable passing from the connector to the power supply.
    So, there is not much room to add a heatsink, maybe a small one, with 5mm height or less or simply a slightly larger heat plate than the chip surface.
    I am thinking about an "L" form heatplate, positioned below the mains connector while the L angle profile would touch
    the chip surpace. Glewed then with isolation and coating on the PCB.

    Only to think about. Maybe at a later moment, I will discover this more.
     
  18. Lennyvalentin macrumors 65816

    Lennyvalentin

    Joined:
    Apr 25, 2011
    #18
    Don't obsess over it. These software temperature readers aren't super reliable or accurate, nor is the hardware the software is sampling either (the diodes vary in sensitivity and need calibration for reliable temp readings; this may or may not have been done, who knows.)

    If there was an issue with these chips it would have manifested itself by now. The thread is several years old, and so far nothing, from what I can tell. So just - err - chill... :)
     
  19. Xde macrumors member

    Xde

    Joined:
    Jul 11, 2016
    #19
    I hope you're right. What we see is a chip that seems running out of specification.
    If this values are real or not, nobody knows.

    But I am not so confident, that Apple does everything as best they can do.
    You can see that many people have problems with their nMP, and Apple is unable to service.
    They have an unofficial repair program for the GPUs (why not official if here problems exists).
    Nevertheless, people with these kind of GPU problems are left in the rain.

    And if I could easily reach this chip, I would set a small heatsink on top.
     

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