New 5k iMac suddenly using 100% CPU and unresponsive

Discussion in 'iMac' started by pward, Jan 11, 2016.

  1. pward macrumors member

    Joined:
    Nov 26, 2008
    #1
    Hi,

    I have had a late 2015 5k iMac for two weeks and on two occasions I have experienced all four cores suddenly using 100% CPU and the system coming unresponsive, requiring a power recycle to resolve. Can't remember what I was doing on the first occasion but on the second occasion just now I had just launched iTunes. Email and Safari were also running but nothing else significant.

    Any thoughts as to what this could be causing this?
     
  2. Samuelsan2001 macrumors 603

    Joined:
    Oct 24, 2013
    #2
    Sounds like a rogue process somewhere, it's two weeks old take it back to apple if you can't find whats causing it, there is no way anyone on here can diagnose it from that description it could be any one of thousands of things.
     
  3. maflynn Moderator

    maflynn

    Staff Member

    Joined:
    May 3, 2009
    Location:
    Boston
    #3
    Fire up the Activity Monitor and see what processes are chewing up your cpu cycles.
     
  4. pward thread starter macrumors member

    Joined:
    Nov 26, 2008
    #4
    Thanks Mike. However it is not possible to run Activity Manager as when it happens the system becomes almost completely unresponsive. iStat Menus shows all four cores at 100% usage and I get the spinning beach ball. It isn't possible to use any apps in this situation.

    I ran the hardware diagnostics and that reported no issues so could be a runaway process causing it. The system is running with a restored Time Machine backup from my Mid-2010 iMac so it could be something carried over that the new iMac doesn't like. I ran Etrecheck and found an older version of Cocktail installed which uses Launch Agents and Launch Daemons - I have deleted Cocktail and all seems well for now.
     
  5. Berlepsch macrumors 6502

    Berlepsch

    Joined:
    Oct 22, 2007
    #6
    You can fire up Console and check the logs if something unusual was happening when your system went into freeze.

    It might also help if you upgrade your applications to the latest versions, if possible. El Capitan brought a number of internal changes like system integrity protection, which might cause some older apps to behave strangely.
     
  6. maflynn Moderator

    maflynn

    Staff Member

    Joined:
    May 3, 2009
    Location:
    Boston
    #7
    Go into the terminal and type top.

    Does the same thing and it may show you what's going on. Even if the machine becomes unresponsive, keep an eye on what's chewing up your system
     
  7. pward thread starter macrumors member

    Joined:
    Nov 26, 2008
    #8
    Thanks. However I actually had Console running at the time (curiosity value from an ageing Unix techie) and it reported nothing unusual when the problem occurred.
    --- Post Merged, Jan 12, 2016 ---
    Thanks Mike. As I couldn't type anything into Terminal when the problem occurred (it was THAT unresponsive) perhaps I should leave 'top' running permanently and visible in case it happens again(?)
     

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