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macOS Sierra CalNCService high CPU usage



  • Don Rowlands

    I'm not a mac expert by any means, but after doing what you said up to the cal internet sync part I noticed that cpu was still running at 100% (+!). I then disabled Google calendar sync in internet accounts, the %age CPU showing in top dropped off immediately.  As I don't need it sync'd with my mac calendar, I'm more than happy to leave it that way.  Thanks for the pointer!

  • Roberto Sonzogni

    To me, happened with sync of Google accounts.
    Solved disabling sync of calendars of Google
    Cpu was again over 100% so I needed those more actions: Logout, Login
    Then I can re-enable sync of Google accounts.

  • Carlos Luz

    Hi. For me, the offender is very objectively iCloud Reminders.

    I tried all of the above, none worked. As soon as I disabled Reminders under Internet Accounts>iCloud, the service went back to normal.

    I do need to sync reminders with my mac but at least I know that this is the culprit in my case. 

  • Ned

    For me, it was a specific reminder causing the issue. I clicked done, and the CPU usage dropped off a few seconds later.

  • Sean V

    For me, both CalNCService and accountsd were running hot. Disabling Google calendar sync in Internet Accounts did the trick. I was able to re-enable it a few minutes later without recurrence of the issue. Thanks all for the tips!


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