Macbook Air overheating results in 1.2 GHz CPU

Discussion in 'MacBook Air' started by Beliyaal, Mar 23, 2008.

  1. Beliyaal macrumors member

    Joined:
    Feb 14, 2008
    #1
    I have been experiencing bad performance watching videos on the Air, and I went ahead and did some digging. I originally was able to observe the CPU:s throttling down to 1.2 GHz when both cores are 100% active with CPU Rightmark in XP.

    This prompted me to read up on how the Intel CPU:s handles thermal throttling and how to read the registers in the CPU that can tell what is happening. So I went ahead and created an app for OSX that reads these registers and reports the real CPU frequency and some other stuff including core temperature.

    The conclusion? The CPU is able to work at 1.8 GHz for approximately 5 seconds before the heat throttling kicks in and it stabilizes at 1.2 GHz.

    It's not possible to read the real temperature of the cores. The CPU will only tell you how many degrees below its maximum operating temperature it operating at. The maximum operating temperature is called TjMax and according to some information from Intel this temperature is calibrated per CPU. For mobile CPU:s however TjMax should be approximately either 100 or 85 degree centigrade depending on a bit set in the registers of the CPU. The Air happens to be rated for 100 degrees so I will use that as a reference.

    What I found was that the CPU starts throttling at about 75 degrees when one core is in use. Using one core fully my core will throttle down to 1.6 Ghz. It seems that when it reaches 80 degrees more aggressive throttling kicks in and with two cores working fulltime the temperature hovers close to 80 degrees.

    At first I wasn't sure that it was thermal throttling that was happening because the CPU registers didn't report that it was currently throttling because of heat, but that turned out to be because AppleIntelCPUPowerManagement.kext caught the interrupts and cleared the bits in question. When I disabled the kext I was able to see that it was indeed thermal throttling that is the issue.

    What I'm interested in now is if all Air:s have these problems. I have put the application that should be considered in Alpha state on my homepage: MSR Tools

    I would appreciate if some of you could try it out on your Air:s and report back how much your CPUs throttle when you are running two terminals with "yes > /dev/null". I cannot guarantee that the Application is totally safe to run, but if you experience a system crash it will not load automatically, so it shouldn't cause any permanent damage. Just make sure you save your documents before trying. The app sometimes crash when you first start it, just press Relaunch and it should load ok. And please don't run it on anything other than an Air, because thats what I have tested it on. The interesting value is the "Actual Frequency" at the bottom of the window.

    This together with the 60 GB SSD is really disappointing. I wasn't expecting to buy a 1.2 GHz laptop with 60 GB HD.

    [​IMG]
     
  2. hotdamn macrumors 6502

    Joined:
    Jan 24, 2007
    Location:
    Ottawa, ON, Canada
    #2
    I was writing some code in C, and my macbook air totally smeared. It was hilarious.

    in other news, do a permission repair; you never know, it might just fix your trouble.
     
  3. anarchron macrumors member

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    Aug 7, 2004
    #3
    Yep, I noticed exactly the same thing on mine.
     
  4. heatmiser macrumors 68020

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    Dec 6, 2007
    #4
    I couldn't resist! I'm running it on my Macbook. Nice app; this is the first 3rd party I've come across that's been able to give real-time updates on the CPU speeds in OS X. If, by chance, you ever write an underclocking application, do share!
     
  5. Beliyaal thread starter macrumors member

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    Feb 14, 2008
    #5
    Seriously? That is not even remotely likely.
     
  6. hotdamn macrumors 6502

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    #6
    Seriously. That's what they told me at Apple.
     
  7. Beliyaal thread starter macrumors member

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    Feb 14, 2008
    #7
    Are you saying that it fixed your issue or are you just pointing out the ludicrousness of Apple support? The issue is the same in XP so repairing permissions isn't going to help with that.
     
  8. jont-fu macrumors regular

    Joined:
    Mar 13, 2008
    #8
    Yes, I get the same result: it quickly drops to 1.2GHz running 2x yes>null, and when I added to that playing a video, it even dropped occasionally to 0.8GHz. The cores can run at 1.6GHz only momentarily. It's like a car engine with a turbocharger; you can't run it for long in full power. I wonder if it would even be possible to transfer all that heat away from the reduced size cpu casing, running continuously at full power?

    A bit disappointing, although I didn't buy the Air for the processing power; it works fine for the stuff I need and overall is a nice machine. At this light it's not really suitable for professional audio/video work or gaming.

    Oh and: Props for the MSR Tool!
     
  9. Sesshi macrumors G3

    Sesshi

    Joined:
    Jun 3, 2006
    Location:
    One Nation Under Gordon
    #9
    Oh come on guys. Why the surprise / disappointment?

    It's a 21st Century Apple. Smoke & mirrors. Style, Compromise and Marketing over Engineering and Function. Seriously, what do you expect? For it to run reliably like a price-comparable Sony? Lenovo? ...Dell?

    Since it happens with every single machine they make these days - at least those I have experience of, which just happens to be every single model in their lineup since '06 - you must be used to justifying to yourself workarounds to make the hardware and software that you believe to be superior to run as it should.

    Apple tells me my Air is working perfectly and it has exactly the same cooling-related issues as evidenced in this subforum. None of you using smcFancontrol on full blast? If I'm doing something that needs to work without jerky interruptions, I only get core shutdowns when I start smcFancontrol after already starting to stress the Air a little. If I have it running all the time at 6.2K I get no core shutdowns and no uncalled-for throttling (unless it's a factor of the power management, or unless I'm somewhere very warm). Of course, in this mode it is noisier than any other ultraportable I have.

    If I buy an Apple nowadays I know it's going to have major compromises apart from the way it looks. And apart from obviously the need to run OS X apps portably at times, that is practically the only reason a crippled-by-marketing machine like the Air got into / is still in my inventory - and given that it's not my main ultraportable anymore, I can live with the compromises.

    Either get a class action going, or download smcFancontrol. Barring a move to cooler IGP/CPU for the next gen, unless Apple starts putting in more effective (and noisier) fan control themselves those are likely to be your only solutions.
     
  10. hotdamn macrumors 6502

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    Jan 24, 2007
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    Ottawa, ON, Canada
    #10
    I'm only half joking.
    sadly, as it turns out, my machine is only acting up when it's plugged in. I can do anything from battery power. weird.

    and to the guy above me: take your pessimistic tooshy outta here ;)
     
  11. Sesshi macrumors G3

    Sesshi

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  12. hotdamn macrumors 6502

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    #13
    a cookie.
    now imagine that melting cookie trying to run your apps.

    yeah, not happening.
     
  13. CaptainCannabis macrumors regular

    Joined:
    Oct 29, 2007
    #14
    Yea, I feel I bought the biggest piece of crap apple has ever made.
    My guess is that they didn't test it enough to address the heating issues, they just wanted it to be out by Jan/Feb.

    Foward this to Apple to see if they can do something about the overheating.
    I've only experienced core shutdowns and reductions in CPU while playing wow on veeeerrry rare occasions, so i doesn't really bother me, but I know there are people who have this problem all the time.
     
  14. Beliyaal thread starter macrumors member

    Joined:
    Feb 14, 2008
    #15
    Unfortunately class action suites are useless in Sweden, and smcFanControl changes nothing, the temperature still reaches 80 degrees.

    When I tried this from a cold computer I noticed that the CPU was throttling even when the temperature was very low. It seems I'm still missing something. Will try the same thing without the Apple CPU management kext later.
     
  15. Sesshi macrumors G3

    Sesshi

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    #16
    For me it doesn't exceed 73C given a heavy load and I don't get unexpected behaviour - but ambient here is 15C.

    The from-cold throttling analysis I can't help with that much, but smcFancontrol (provided that you're running it full blast all the time) does definitely help with thermally induced issues.

    No. You just bought another (beautiful) piece of crap Apple has made.
     
  16. Darge13 macrumors newbie

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    Feb 18, 2008
    #17
  17. Beliyaal thread starter macrumors member

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    Feb 14, 2008
    #18
    So you Air is running at full speed at full load if you check it with MSR Tools?
     
  18. sir. mac macrumors regular

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    Nov 21, 2006
    #19
    Tried it on my 1.6 80hdd and on full load both cores quickly came down to 1.2 stable (this was with office word on + two terminal windows on full load), with the occasional spike up to 1.4.

    Did anyone with 1.8 try this?

    I reckon Apple will fine-tune this in further updates. And if not, 1.2 suits my needs for now anyway. Will consider the next gen MBA though, since Penryn probably will be a better fit re heat.
     
  19. NC MacGuy macrumors 603

    NC MacGuy

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    The good side of the grass.
    #20
    '06- Or since the hasty switch to Intel? I actually agree with you on many levels but until there's a way to run OSX or MSft actually puts out a better OS, I'm kinda stuck.

    XP was usable and I was hoping Vista would entice me to switch to a wider range of hardware offerings.

    Don't have time for Linux so Apple it is. Flaws and all.

    It gets 90% of my simple needs of word processing, mail, spreadsheets, browsing done but beyond can be hit/miss. I have plenty of Suns to play with for beyond.

    I have not drank the koolaid and the RDF hasn't had an affect on my sensibilities as you've alluded.
     
  20. Sesshi macrumors G3

    Sesshi

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    #21
    Perhaps you should edit your posts to reflect that? And despite how you may feel about the pitch of my posts, it's not all about you, you know. There's plenty more where you came from :p
     
  21. NC MacGuy macrumors 603

    NC MacGuy

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    #22
    That wouldn't be any fun now, would it?:D

    You know not from where I come....
     
  22. purplewarlock macrumors member

    Joined:
    Jan 31, 2008
    #23
    I kept yes running for about 1 min and CPU dropped from 1.6 to 1.4 on both Cores by that time, but didn't go any lower (see attached photo).

    However something relating to this is that I think some of the behavior and heat issues are Mac specific. I posted to another thread and mentioned I can run World of Warcraft fine on the exact same computer under Windows XP Bootcamp with much less heat issues than on OS X.

    So I think there is a combination of things going on. I recommend anyone having youtube or DVD playback issues try the same task under bootcamp under Windows if you happen to have it installed just for curiosity sake, I think you'll find it runs much better with better graphics performance for sustained periods of time with about 5 degree less temperature. For even further performance benefits, under Windows you can undervolt using RMClock.

    So I'm not sure how much of the heat problems are hardware related versus OS / software device driver related issues, my experience indicates the hardware is fine but OS X or other Apple specific driver software may be the culprit as opposed to the heat sink design, the CPU itself, etc.

    edit: I forgot to mention this is for the 1.6/80GB version of Air with all the latest software updates.
     

    Attached Files:

  23. NC MacGuy macrumors 603

    NC MacGuy

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    #24
    ^ Bingo!

    I think you are truly on to something. Not the first post of max. heat & shutdown/throttling w. OSX and fine w. BC & Windows.
     
  24. bcaslis macrumors 68020

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    Mar 11, 2008
    #25
    Why do you all assume this is due to heat? It's standard to lower clock frequencies as part of power management. That's obvious from those that see the CPU cycling down when the part isn't hot.
     

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