Something is cooking my macbook

Discussion in 'macOS' started by lucas, Aug 16, 2008.

  1. lucas macrumors member

    Jun 6, 2005
    My macbook has been running quite hot recently, the fans are fire up about 10 seconds after booting up and never go off. temperatures are around 70ºC with no apps running. running Top and Activity Monitor reveal nothing using much cpu (top and activity monitor are at the top of the usage list and neither is using more than 4-5% cpu), and total cpu load is around 5%.

    I installed a fresh copy of leopard on an external drive and found the problem disappeared, so it's definitely a software issue. booted of the external drive I was able to run the laptop for over an hour without it getting hot to touch, and the fans were inaudible.

    I use the "Better Energy Savings" energy profile, with the only change being that I set it to never put the computer to sleep. the only way I can think of that the thing would generate so much heat while doing so little would be if the cpu wasnt throttling itself properly, but I dont know where to look to see if that's the problem.

    Can anyone tell me what else I should try? I dont think I should have to reformat the notebook to fix this.
  2. kolax macrumors G3

    Mar 20, 2007
    Let me understand this now - the problem doesn't exist anymore after you reinstalled Leopard, but you are curious as to what was causing it?

    See when you loaded up Activity Monitor, did you go to show "All Processes" like shown below? It wouldn't display any system related processes otherwise. I sometimes used to encounter a system process taking up a lot of CPU usage, causing fans to come on full blast, but I haven't had this since Mac OS X 10.5.4 was released.

  3. lucas thread starter macrumors member

    Jun 6, 2005
    not quite, I installed leopard on an external drive (in a FW enclosure) and on that install everything was peachy.

    yes, I had everything showing. I also check with cmd line tools "top", and "ps aux" and nothing is showing up as using the cpu at all. all signs are pointing to cpu throttling not working as expected any more. I found a tool called CoolBookController which shows me the current CPU frequency, which confirms that it's sitting at 2.0 ghz when idle (and it's only a 2.0ghz mb).

    does anyone know if there is a single .kext is responsible for this? seems like the easiest way to fix it would be to upgrade the external hdd fresh install to 10.5.4 and then replace the offending .kext on the internal hdd
  4. lucas thread starter macrumors member

    Jun 6, 2005
    I updated the external hdd install to 10.5.4 and the thing started running hot again, and coolbook showed that throttling had quit working and it was sitting at 2GHz while idle.

    by this point I was getting a bit frustrated, and decided to do something that I expected would either kill the installation or have no effect at all. I deleted /System/Library/Extensions/AppleIntelCPUPowerManagement.kext and rebooted. on shutting down it updated it's boot caches and on rebooting it seemed to be running cooler and the fans quietened down.

    coolbook showed it as running at 1.675ghz, and the different power saving modes had no effect. just to see what would happen I then copied the AppleIntelCPUPowerManagement.kext from the internal hdd to the external one and rebooted. again the boot caches got updated, and to my delight on starting up again cpu throttling was working correctly. coolbook shows me that now when idle the cpu is only running at 1.0GHz, and if i run "cat /dev/random >> /dev/null" it ramps straight up to 2.0GHz as expected.

    It seems like the bootcache just needed to be re-jiggered to get it working again, although I have no idea why it happened in the first place on the clean install that had nothing other than the 10.5.4 update done to it. I have since repeated the "remove, reboot, replace, reboot" steps on the installation on the internal hdd with success.

    I hope this info might be of help to anyone else who ends up in this strange situation.
  5. lucas thread starter macrumors member

    Jun 6, 2005
    well, it turns out the fix wasn't permanent. I rebooted the notebook and it went right back to being stuck on 2GHz.

    after repeating the remove/reboot/replace/reboot steps again speedstep is working again. I guess I'll try and avoid rebooting, and maybe give applecare a call :/

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