OSX CPU Usage.

Discussion in 'Mac Apps and Mac App Store' started by Neil Parfitt, Nov 21, 2006.

  1. Neil Parfitt macrumors newbie

    Nov 20, 2006
    I'm exporting a rather hefty iMovie project that is about 1 and a half hours long.

    I find it puzzling that Activity Monitor is only showing an average CPU usage of 104% for iMovie, and 68% of CPU muscle is just sitting there idle.. giving me an estimated 'compressing movie time of 306 minutes' ! It's not like that machine is really crunching through this.. the hard drives are averaging 700k/sec read.. and an occasional write.

    Is there a way in OSX to force an application to use as much CPU as possible? This would take half the time if iMovie really utilized the CPU's to their full potential.


    Neil (2.66 MacPro, 10.4.7)
  2. davidjearly macrumors 68020


    Sep 21, 2006
    Glasgow, Scotland
    I'm sure there are others that know better, but I don't think there is a way you can force an app to put more 'strain' on the CPU. Obviously the system is designed with stability in mind and whilst it might seem as though your CPU is being under-utilised, it is likely to do with system stabililty.

    Maybe someone else can help more though.

  3. gr8tfly macrumors 603


    Oct 29, 2006
    ~119W 34N
    A process can be "reniced" to change it's priority. That doesn't mean it will get the higher priority, though.

    I don't know enough about the internal workings of iMovie, but an application gets it's processing allocated to each CPU core based on multi-threading. So, if there is only one thread doing the bulk of the work, it's not going to get much help from the other processor core(s). I'm sure iMovie isn't that simplified (like not being multi-threaded), but there may be one portion of the rendering that almost entirely resids within one thread.

    Hope I hit the right level of technoblabble to help. Although, at 0130 PST, nut sure how much more I could muster.
  4. Sharky II macrumors 6502a

    Sharky II

    Jan 6, 2004
    United Kingdom
    This happens because when you're exporting/bouncing, it only really uses one thread.

    Same happens in Logic Pro when you bounce/export a song - i wish it would use both/all processors fully and get it done quicker... but it just doesn't...

    It's writing to a single file, so is probably just using one intense thread - perhaps they could optimise this, i don't know.


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