Can I underclock the MB to maximise Battery life?

Discussion in 'MacBook Pro' started by dingdongbubble, Aug 28, 2007.

  1. dingdongbubble macrumors 6502a

    Jun 1, 2007
    Lets say I want to read a PDF book in bed comfortably and doze off to sleep. Now is it possible for me to underclock the Macbook to say 1 Ghz or maybe switching off one core so that the thing runs cool, battery life goes upto say 7 hours or so. I wont be taxing the system.

    So is this possible?

    A side question: I was looking at a Sony Vaio and it had two modes. 1 with a dedicated GPU on and the other with the Intel integ GPU. The Intel GPU allowed the Pc to run for around 7 hours I think whereas the dedicated GPU made the battery life upto 3-4 hours like normal. So why is it not the same with the MB? Why is there no 7 hour battery life? It would be an AMAZING marketting point from Apple.
  2. jrodatus macrumors member

    Aug 5, 2007
    First your first question, check out CoolBook -- it can underclock to as low as 800Mhz, though it does cost a dime.
  3. mkrishnan Moderator emeritus


    Jan 9, 2004
    Grand Rapids, MI, USA
    Speed reduction: There are more sophisticated things you can do, but for starters, Sys Prefs -> Energy Saver. Select the situation you want to specify options for and then go to the options tab. At the bottom you can put the processor in reduced mode. There are more sophisticated things you can do; I know with the developer tools, you can turn a core off.

    Two GPU modes: Well, the obvious answer would be, because the Macbook does not have a dedicated GPU to which it would switch for more processing prowess, but I'm not sure what you're looking for. ;) The Macbook is already using the Intel GPU to get the amount of battery life it gets now.
  4. dingdongbubble thread starter macrumors 6502a

    Jun 1, 2007
    Wirelessly posted (Mozilla/5.0 (SymbianOS/9.1; U; en-us) AppleWebKit/413 (KHTML, like Gecko) Safari/413 es61)

    If i make my MB as slow as possible without voiding the warranty, how many hours of battery life do you expect?

    secondly will turning off a core using xcode void my warranty? Where can i find a tutorial for this and does it really increase battery life alot?

  5. brettanderson macrumors member

    Jun 26, 2007
    This is a useful tip! Are there other tricks people know about.
  6. dingdongbubble thread starter macrumors 6502a

    Jun 1, 2007
    Hey plz tell me how do you use Developer Tools to switch off a core.
  7. TBi macrumors 68030


    Jul 26, 2005
    Turning a core off can result in increased power consumption because instead of two processors running at very lower power, you have one processor running a high power.
  8. brettanderson macrumors member

    Jun 26, 2007
    Yeah I just turned off a core and my power comsumption went up for this reason.

    If you want to try for yourself install the program CHUD from the xcode developer tools folder on your tiger install DVD. Then go to system preferences and click on the processor icon.
  9. NJuul macrumors 6502

    Mar 15, 2006
    You cannot manually set the processor speed on intel macs (at least not that I know of), nor is there a "reduced mode" option in Energy Saver.
    The Intel chips automatically adjust the processor speed depending on the overall system load, you can monitor this with a number widgets and small programs, like iStat pro.

    However, you can turn off a core using CHUD, which is one of the developer tools located on your install discs. When you install it, it creates a new system preference (Processor), and optionally places an icon in your menubar where you can turn a core on/off (picture).

    However, as said by TBi, turning a core off makes the system run the other at full speed, which then heats up, and actually decrease your battery life.

    Attached Files:

  10. dingdongbubble thread starter macrumors 6502a

    Jun 1, 2007
    So why cant I switch a core AND lower the power from the active core?
  11. koobcamuk macrumors 68040


    Oct 23, 2006
    get an ibook :)
  12. Sesshi macrumors G3


    Jun 3, 2006
    One Nation Under Gordon
    You'll only get those endurances from a ULV.

    I have the (pre-Santa Rosa) SZ4, and the battery life is not a strength of this machine. Even with the GMA enabled and power management enabled, it only goes for about an hour longer than the MBP, which is middle of the road as far as runtime goes among laptops of this type (and with the NVidia GPU enabled, it goes only for a smidgen longer than the MBP with similar power saving measures). The difference with the SZ is that you can put an extended battery on it which gives it respectable runtimes, an option not available with the MBP.
  13. ElCamino macrumors member


    Mar 5, 2006
    What you can also do is; if your just reading a PDF file or working on word, excel, etc... that doesn't require access to internet, turn off the Airport, and also turn off the Bluetooth. This will give you some extra time.
  14. Sesshi macrumors G3


    Jun 3, 2006
    One Nation Under Gordon
  15. Corrosive vinyl macrumors 6502

    Corrosive vinyl

    Sep 22, 2006
    as stated above by many others....
    1. get an iBook (or another single core laptop)
    2. turn off all unnecessary processes AND apps... if they are on they use RAM which results in heat and energy consumption... good point on the airport and bluetooth which like using RAM (ie: windowserver)
    3. don't worry about it much... after all if you use energy saver and turn off unnecessary things you will get as much as you can get out of energy savings. don't spend energy on trying to save it... it is kind of counterproductive

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