Macbook Pro 15 remains COOL, but CPU hits 100 C 212F

Discussion in 'MacBook Pro' started by hundert, Jan 24, 2010.

  1. hundert macrumors regular


    Jan 24, 2010
    Hi, I am new to forums. A very nice place I must say. I have stopped here before, as I looked for answers to my questions, and I had no problems finding threads related to my problems. But here's what I have.

    I have tried every possible Temperature Monitoring program installed and as it looks, my CPU A Diode showes 212F (100C), when computer is doing heavy work (games, FinalCut, extracting big files). The funny thing: my computer is COOL on touch, it is barely warm, even if it works for hours under the mentioned temperature.

    My attempts to solve it were:
    -I cleaned Macbook Pro inside. Every fan is clean, under Logic Board is clean.
    -I applied new Thermal Paste containing silver. A very good one.
    -I always had SMC FanControl Installed and often work at 6000rpm
    -my mac is slightly elevated, there is a good airflow underneath it.

    CPU temps are still reaching 100, while the rest of laptop is between 35-45C (90F-113F) when doing heavy work. Main heatsink it says 45-46C (114F)

    Can it be a crappy diode?

    By the way, the temp has always been like this, since 2007 and I never had problem with my mac. But 100C is not normal! At least, others say.

    My 17 Macbook Pro is WAY cooler.

  2. csdibiase macrumors member

    Jan 1, 2010
    Cleveland, OH
    Yeah 100C is generally speaking out of spec for any intel chip. I'd check the fan and make sure it's spinning up enough at load. Either that or perhaps the heat pipe in the heat sink assembly failed. Without that you're relying on pure metal conductance to pull the head off the die and to the sink.
  3. Sneakz macrumors 65816


    Jul 17, 2008
    Toronto, Ontario, Canada
    100°C is within spec of almost all of Intel's modern mobile processors. It's a high temp, but it's within spec.
  4. rwd hero macrumors 6502

    Aug 6, 2008
    Baltimore, Maryland
    This may be completely different between my machine and yours, but while gaming i only usually hit 195F ish.
  5. Pax macrumors 6502a

    Dec 12, 2003
    Mine gets up to just over 100 C during heavy use. (2.26 Core2Duo 13 MacBook Pro). It's just within Intel spec, I think the CPU is rated to 105 C.

    I think Apple has designed it right to the limit.... if you watch the fans they don't kick in until the CPU is into the 90's and then ramp up to hold it just below the Intel spec.

    On mine there is about a 20 C difference between the CPU core temp and the heatsink temp. I think that's pretty good considering the small thermal junction between the two and the fact that the core is dissipating 35 (?) Watts. I did the calculations assuming a good thermal paste value and the size of the die, and it all seemed about right.

    So Apple seems to have designed right to the Intel limit, fair enough. Pretty damned hot in there though, I wouldn't disagree!
  6. Chwisch87 macrumors 6502

    Sep 30, 2008
    Well MacBook Pro's run very hot because they are used in studio environments where the fans can't be all that loud. In most situations a processor can run that high but I wouldn't expect it to last much beyond 5 years at 100c. I mean you can run a processor that hot but instead of 25 years of life you get something like 5 to 7. Now the issue is that you probably just have a bad CPU. Not all cpu's from the wafer are equal. Some over clock a lot better than others etc. Some run cooler than others.

    If you computer is still in warranty with apple care i would probably just try to get apple to replace it.

    My MBP gets to about 82c in max cpu load so i can understand where you are coming from. If anything I would throw a solid state in mine and underclock the CPU down to 2.2 instead of 2.5 to get the temps down a bit.
  7. cluthz macrumors 68040


    Jun 15, 2004
    When my MBP reaches 90-95°C it's really hot to touch.
    Also the heat sink monitor and cpu diode monitor should read within 10-15°C of each other.

    If heat sink is 45°C I suspect the CPU to be no hotter than 65°C.
    I'd try the apple hardware cd tester.
  8. Pax macrumors 6502a

    Dec 12, 2003
    I looked at my 13 Unibody MBP under full load and noted the following:
    - Delta temp between CPU and heatsink is always about 20 C
    - CPU temp rises to 103 C before the fans really start to kick in (this takes 5 minutes)
    - Fans increase gradually to bring CPU temp back down to about 90 C after 15 minutes

    The fan control strategy makes sense to me - Apple is happy to run the CPU up to its 105 C spec limit, but not let it sit there indefinitely. I guess most CPU loads are transient, so there's no point in turning the fans on too early, better to wait and see whether the core slows down again rather than blasting the fans too early.

    The spec for the Core2Duo temperatures is 105 C, not sure if this is the right model but here's a link....

    The CPU is entirely fail safe. There's lots of useful info here....
    There are two states to search the PDF for:-
    PROCHOT# - lowers the clockspeed if CPU gets too hot
    THERMTRIP# - trips the CPU out completely if it gets really hot
    These are both internal to the CPU, Apple can't mess with them.

    My first CoreDuo Macbook had a problem with this, PROCHOT got invoked and the CPU dropped from 1.86 down to 1.5 (IIRC) GHz. I think there was even a class action suit against Apple, it was so common.

    A few questions for you
    - does your CPU temp ever exceed 105 C, particularly during the first few minutes under full load before the fans ramp up?
    - do your fans ramp up to a nice high speed after 10-15 minutes at full load?
    - does your CPU ever lower its clock speed (you used to be able to use CoreDuoTemp for this, not sure how else you could do it)
    - does your Mac ever crash (black screen) indicating THERMTRIP has been reached?

    I would say that if PROCHOT state never occurs, the CPU is perfectly happy and don't worry about it. If PROCHOT is occurring, you might want to re-do the thermal paste or find out if the heat pipes are dead???
  9. Eidorian macrumors Penryn


    Mar 23, 2005
    Here's a good bit of information.

    Now if it was only required reading.
  10. Pax macrumors 6502a

    Dec 12, 2003
    Thanks Eidorian

    I checked my MBP and it doesn't go into PROCHOT#. I ran two Matlab FFT loops to fully load both cores and the time for each loop didn't change as the CPU heated up to 102 C and then stabilised at about 90 C. The clock speed didn't change, so presumably PROCHOT# didn't occur.
  11. hundert thread starter macrumors regular


    Jan 24, 2010

    Never over 101, but always over 98 under heavy load.
    yes fans reach 6000 even if I dont use smc, but they keep temp around 100.
    no, cpu does not load its speed.
    Mac crashed a few times during left 4 dead on bootcamp winxp, but I dont know what temp it had.

    by the way, that mac of mine just died today. gpu failure it seems.
  12. Pax macrumors 6502a

    Dec 12, 2003
    Well that has solved the problem in one way :(

    I think Apple offered an extended warranty on those models because of the acknowledged GPU problem - perhaps you can get it fixed/replaced even if you don't have Applecare???? Hopefully that will also cool your CPU.
  13. hundert thread starter macrumors regular


    Jan 24, 2010
    Thanks, Pax

    that macbook died. This thread continues here:

    I will inform, if I got it replaced for free.

    No need to continue this thread, I got all answeres I needed.

    Thanks everyone!

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