Effect of 1 Core on Battery Life?

Discussion in 'MacBook Pro' started by darwinian, Jan 2, 2009.

  1. darwinian macrumors 6502a

    darwinian

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    Jan 4, 2008
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    In R4, more or less
    #1
    Does anyone know if the power consumption for the CPU goes down drastically when 1 core is disabled (via CPU.menu extra/processor palette/prefpane)?

    I've read two conflicting reports. One anecdotally stated that battery life increased (my hope and expectation) and another said that it may actually decrease battery life (but had a poor argument for it).
     
  2. kastenbrust macrumors 68030

    kastenbrust

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    North Korea
    #2
    Why dont you test it?
     
  3. G.T. macrumors 6502a

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    Jul 12, 2008
    #3
    I'm not sure if 'drastically' is the right word. On first reading my thought would have been of cause it would decrease, however, if you think about it now one core is disabled the other has to be used twice as much now, therefore drawing more power than you'd think. Although it will only draw enough to power that single core for as much power as it needs so you would see a decrease but how much will vary (if any decrease).
     
  4. kastenbrust macrumors 68030

    kastenbrust

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    #4
    Its not that simple, the other one doesnt have to be used twice as much, because two cores are only used on applications which have multicore support like the game Crysis etc. So disabling a core probably wouldnt make any difference to the battery life, maybe give you an extra few minuets.
     
  5. FF_productions macrumors 68030

    FF_productions

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    Mt. Prospect, Illinois
    #5
    From what I've heard over-time, it could run down the battery more then having 2 cores. You're putting more stress on 1 core rather then splitting the workload between 2.

    Display brightness is a huge factor along with wireless and what apps you are running. I wouldn't worry about shutting any cores down, it's as efficient as its gonna get processor-wise.
     
  6. G.T. macrumors 6502a

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    Jul 12, 2008
    #6
    Yeah I agree I forgot that applications need multi-core support
     
  7. darwinian thread starter macrumors 6502a

    darwinian

    Joined:
    Jan 4, 2008
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    In R4, more or less
    #7
    Yeah, the trouble with battery tests is that they're time consuming and difficult to control. I might do it, yet.

    I was hoping someone knew the power draw from 1 core versus 2, if it changes.

    It's also my understanding that multithreading can take place on one core - apps have been multithreaded for a long time and can be talked about independently of the number of cores, even though it's also true that multiple cores can aid the efficiency of multithreading.
     
  8. J the Ninja macrumors 68000

    Joined:
    Jul 14, 2008
    #8
    Unless the CPU supports hyperthreading, there is a strict limit of one thread at a time. As for power, iStat Menu has a readout of your CPU power usage. My guess is you'd save around 10w during heavy multi-theaded number crunching...enough to buy maybe 20-25% more battery life. Of course, at the expense of running the system longer, plus everything else that needs to be run longer, so in the end I doubt you'd really come out ahead.
     

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