%CPU usage

Discussion in 'MacBook Pro' started by sdneidich, Mar 12, 2011.

  1. sdneidich macrumors member

    Joined:
    Feb 5, 2011
    Location:
    NC, USA
    #1
    This caused some confusion for me, so I wanted to share with everyone.

    Observation
    While ripping some DVDs using HandBrake, I realized my mac was using a lot of system resources. I opened up Activity Monitor, and much to my surprise, the % CPU being used by HandBrake was ranging from 340 to 390 (!).

    How was this possible? note: Core i7 processor, dual core 13 inch

    What I think is the Answer
    The i7 in this laptop is dual core, and has hyperthreading enabled. This means that the computer can operate as if there were 4 cores.
    The process HandBrake is making full use of the hyperthreading (in fact, it displays at 24 threads) and is therefore maximizing the use of the processor.

    Since up to 4 virtual cores can be maintained, the maximum % CPU usage is 400, not 100.


    Can anyone with a more extensive knowledge of the subject confirm this?
     
  2. darknite38 macrumors regular

    Joined:
    Nov 18, 2010
  3. wordoflife macrumors 604

    wordoflife

    Joined:
    Jul 6, 2009
    #3

    I believe you are correct. I think someone on the forum pointed out to me that OS X counts each core out of 100%, so dual cores it out of 200%, quad is out of 400%.
     
  4. grahamnp macrumors 6502a

    Joined:
    Jun 4, 2008
    #4
    Yes you are correct, 100% x 2 because it is dual core and then multiplied by two again because it can handle two threads per core (hyper threading).
     

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