Ambient temp sensor on 09 Mac Pro

Discussion in 'Mac Pro' started by rexie, Sep 10, 2009.

  1. rexie macrumors newbie

    Joined:
    Nov 17, 2007
    #1
    Hi All,
    My Mac Pro 1,1 was stolen and was replaced with a 2.66 Oct '09 Mac Pro. Have noticed that the temp sensor is way off, up to 8 deg C! My old Mac was accurate for ambient temp no matter what the load was on the computer. On the new Mac on startup it's 2 to 3 degrees too hot then increases. Anyone know where the sensor is?
     
  2. inigel macrumors regular

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    #2
    Not to pick or anything, but how did you determine it was inaccurate?
     
  3. seadragon Contributor

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    Mar 10, 2009
    Location:
    Toronto, Canada
    #3
    Mine is also quite inaccurate. Room temp is 22C and ambient reads 31C.
     
  4. UltraNEO* macrumors 601

    UltraNEO*

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    Jun 16, 2007
    Location:
    近畿日本
    #4

    Unless Apple changed it, the ambient temp sensor should be in the top section, above the optical drive (at least that's where it is on the 08 MP).

    This area should be the coolest part of the MP. Take out the optical caddy and look, it's black and glued to the case!
     
  5. Eithanius macrumors 65816

    Joined:
    Nov 19, 2005
    #5
    @inigel

    Because we have 2 Mac Pros with the right software to compare.

    TS,

    I noticed the same problem here. I had a MacPro2,1 before it got replaced with a MacPro4,1. Basically the ambient temperature on the new Mac Pro registers a higher ambient temp compared to the older model. 27 degrees C on the old MP against 35 on the new...
     
  6. UltraNEO* macrumors 601

    UltraNEO*

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    #6
    Out of curiosity, why is it important?
     
  7. Eithanius macrumors 65816

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    Nov 19, 2005
    #7
    Out of curiosity of course...
     
  8. justflie macrumors 6502a

    justflie

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    Nov 29, 2005
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    #8
    I would assume that the case fans' rpms are tied to ambient temp in the case. If it's significantly higher, the fans would probably speed up unnecessarily.
     
  9. ManiG macrumors member

    Joined:
    Aug 11, 2009
    #9
    Same "issue" here, 2009 MP. The ambient consistently shows 6-7 degrees Celsius above the "actual" ambient temperature in my office.

    Not important though, as mentioned just a curiosity. :)
     
  10. UltraNEO* macrumors 601

    UltraNEO*

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    #10
    Since it's attached to the inside of the case, how about attaching a thermo sensor to the exterior of the case? Say under the handle above the optical drive, that should be the direct opposite side, no?

    Actually, I wouldn't be surprised the ambient temps to be higher than room temps, this is because it's the highest part of the enclosure; physics tells us heat rises.
     
  11. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #11
    Ambient may be the internal air temp of the MP, not the room, depending on specific location. At the top of the case makes the least sense IMO, as that's not what being drawn across the cooler/s.

    Ideally, I'd think they'd have placed the sensor in the intake section (just after front fan/s) for the CPU/s to get the most accurate reading, and applicable to the air entering the CPU coolers.

    Fans should be tied to the core temps, not ambient btw. ;) The reason is simple. Cold ambient, say during winter, yet the cores are roasting (really hot under full load). If the fans are tied to the cold air, they won't ramp up, starving the coolers for the cold air needed during the high load period. :)
     
  12. Tesselator macrumors 601

    Tesselator

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    Jan 9, 2008
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    Japan
    #12
    I think they got it right and the Ambient sensor should be right where it is. The ambient sensor tells the system that the exhaust fans are ejecting enough heat or not. If they aren't the heat at the top will increase to considerably above room temp. If they are then Ambient will be within a degree or two of the room temp.

    The CPU (or RAM, HDD, et.) fans are in charge of cooling that part. If that used (heated) air isn't being ejected fast enough then the above sentence kicks in.
     
  13. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #13
    I was thinking in terms of the CPU/mem chamber. Ambient in the intake fan region, and of course the CPU core diode as well. If exhaust heat cycles around internally, the core sensor will pick it up (gets sucked back in the cooler/s), and kick in the exhaust setting, even if ambient hasn't shifted at all. It's not that complicated actually.

    A simpler design is to monitor the overall case temp, which is likely what they're doing (also cheaper). But given the different chambers, you'd really need one per to get accurate data for each, and controll any intake and exhaust fans for each as well.
     
  14. rexie thread starter macrumors newbie

    Joined:
    Nov 17, 2007
    #14
    Thanks for the replies.
    To be honest, the reason I asked is I like seeing the room temp in the menu bar! I could buy a cheap temp sensor and sit on my desk but I didn't need to with my old Mac pro. Don't like this hyper-threading either with current programs, but that's another story!
    Cheers.
     
  15. nanofrog macrumors G4

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    May 6, 2008
    #15
    That's what I do anyway. :)
     
  16. slicecom macrumors 68020

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    Aug 29, 2003
    Location:
    Toronto, Canada
    #16
    Same issue here. My MacPro 1,1 is accurate and my bosses MacPro 4,1 in the same room reports the ambient temperature consistently up to 7C higher than reality (and the accurate temperature on my 1,1).
     
  17. adrianking macrumors newbie

    Joined:
    Mar 25, 2013
    #17
    Mac Pro 2008 model fans going bonkers...

    Thanks for all your posts. I have a Mac Pro 2008 model whose fans are going bonkers, all the time, and it looks like what you've been talking about may what's causing it. I do live in a hot climate and its summer, so it may have tipped the fans to run on full blast all the time. I'll check to see if the real ambient temperature and sensor reading are different.

    I found an app that claims to be able to adjust the temperatures that the fans kick in at. Do you think that doing this to stop my fan kicking in would be dangerous, if I find out that there is a big difference between the real and sensed ambient temp? The computer does not seem to be running hot, and the fans run full bore even when starting up the computer after its been off all night.

    Thoughts appreciated...
     
  18. bax2003 macrumors 6502a

    bax2003

    Joined:
    Dec 25, 2011
    Location:
    Serbia
    #18
    It is logical that temperatures inside chassis are higher than ambient room temp. Inside small volume object (20cm x 50cm x 50cm) you have CPUs, GPU, PSU, LogicBoard and so on which generate heat.

    I would not worry too much, unless fans are too loud for some good reason.
     
  19. DanielCoffey macrumors 65816

    DanielCoffey

    Joined:
    Nov 15, 2010
    Location:
    Edinburgh, UK
    #19
    Fans running full speed imply there is a fault.

    When did you last give your MP a real thorough clean? I mean sliding out all the trays and drives and air-can cleaning the heat-sinks and crevices.

    You might also have an underlying fault so twiddling with fan minimum speeds would not be advisable.

    You will also probably get told to do SMC and PRAM resets so look up the details and do those anyway.
     

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