how do you turn off one of the cores on the MacBook?

Discussion in 'Mac Pro' started by mac000, Jul 14, 2006.

  1. mac000 macrumors 6502a

    Sep 6, 2005
    I leave my computer on during the day when I'm not home and I would also like to leave the MacBook on but it sure gets toasty. I know I dont need 2 cores running at once during the day while the computer isn't doing much.

    Anyways, how do I go about this?
  2. WildCowboy Administrator/Editor


    Staff Member

    Jan 20, 2005
    If you download CHUD tools from Apple's Developer site and install them, you should then be able to shut down a core through System Preferences.
  3. Makosuke macrumors 603

    Aug 15, 2001
    The Cool Part of CA, USA
    Just installing the Developer Tools off of the DVD that came with your Mac will give you the Processor Preference Pane, which will let you disable a core.

    That said, I'm pretty sure this is actually counterproductive: First of all, I think it just disables the core, it doesn't actually power it down--so it's still idling anyway. Further, when I do this, the remaining core kicks up to the full speed, rather than throttling down when not under load. This makes it actually run HOTTER when not under heavy load.

    For example, on my 17" MBP, the cores usually idle (internally) around 57C, and are running at 1.67GHz to save power. When I disabled one core, the speed ramped up to the full 2.16GHz and temperature climbed to about 63C because of the extra power draw. Exact opposite of the desired effect.

    The only time I could think of this doing you any good is if you had something running all the time that ate up as much processor was available, in which case killing one core would limit it to running half as fast. Even then, I'm not sure if you're actually saving any power on the second core or not--their "naps" (assuming the Core Duo even has a feature like that, which I'm not sure it does) might be synchronized.
  4. Eidorian macrumors Penryn


    Mar 23, 2005
    It is counterproductive. The two cores rev down when idle. When you switch to one core it goes to full speed.
  5. mac000 thread starter macrumors 6502a

    Sep 6, 2005
    oh darn, i see. Yea my macbook gets pretty toasty if i leave it on all day. Anyway to tweek it so its not running at the highest/normal level of power?
  6. apunkrockmonk macrumors 6502a


    Nov 20, 2005
    Rochester, NY
    If your worried about heat and its truly idle and not doing anything.... put it to sleep.
  7. Littleodie914 macrumors 68000


    Jun 9, 2004
    Rochester, NY
    That's a possible solution. I just got my Macbook Pro last night, and have noticed that it does get a bit toasty. (Nothing to worry about, but a tad hotter than my iBook.) What if, for example, you wanted to leave your laptop on while you're out just to make sure that your Instant Messenger account stays on? I was a bit bummed when I opened the Energy Saver preference pane and saw that the "Processor Performance" pull-down menu was missing. (Like Reduced, Automatic, Highest.) To the OP though, I too have heard that disabling one of the cores not only increases heat, but also drops battery life by just a bit. :(

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