Late 2015 iMac 5K Freezing

Discussion in 'iMac' started by AdiosVista, Mar 15, 2016.

  1. AdiosVista macrumors 6502

    Sep 10, 2008

    I recently bought a new iMac 5K and am running into a freezing issue. Any help troubleshooting would be greatly appreciated. Here's the info I have:

    • Late 2015 iMac 5K 27"
    • 4 GHz Intel Core i7
    • 24 GB RAM (4 GB x 2 factory, 8 GB x 2 OWC)
    • AMD Radeon R9 M395X 4 GB
    • 512 GB SSD
    • El Capitan 10.11.3

    What happens is I'll be using the iMac under normal conditions (browsing web, writing documents, etc. — nothing intensive like gaming) and the screen will freeze completely. Open windows can't be moved, the dock items don't open or animate, even the clock's time freezes. The only thing that still works is I can move the mouse around the screen but can't click on anything, nor can I switch spaces. My only option at that point is to do a hard shutdown by holding the power button.

    This happens about once every 2 weeks.

    After restarting, I immediately check the Console's error logs and see two that stand out:


    ("TODAYS_DATE_COMPUTER_NAME" is placeholder for what actually appears there)

    I'm not educated in reading these type of error logs but in looking at the Kernel file, some of the key info appears to be:

    • Event: GPU Reset
    • Hung Channels: GFX
    • Pending Command from: UnknownCtx
    • GPU Debug Info (which is unreadable)

    And in the WindowServer file, some highlights are:

    • Command: WindowServer
    • Parent: launchd [1]
    • Event: service progress watchdog
    • Fan speed: 1202 rpm
    • Then in the Timeline format stacks, I see a lot of reference to the CoreGraphics, CGXServer, and WindowServer

    Additionally, I noticed that sometimes when I hard restart from these crashes, iTunes shows a "glitchy" black bar over the scrollbar that jumps and shifts as I cycle through music albums. This appears to eventually go away but definitely looks like something wonky going on with the graphics.

    I did also run the Apple Hardware Diagnostic test and no issues were reported.

    Based on the above info, is anything standing out as the obvious culprit? And yes, I do have AppleCare, but this is my work computer and to bring it in for repair is quite an extensive process. Ideally, I'd like to first troubleshoot the problem before making decisions about returning or having it looked at by Apple. Thank you for your time!
  2. hkoster1 macrumors regular

    Jul 29, 2012
    The Netherlands
    You could try reinstalling OS X (reboot while holding Command-R, then choose to Reinstall OS X), which leaves user folders intact. This solved a similar problem on my 2014 iMac 5K Retina. AppleCare said that the problem may have been caused by a damaged file in OS X in the original installation.
  3. keysofanxiety macrumors G3


    Nov 23, 2011
    Honestly, it sounds like GPU failure. Plus there's massive evidence to suggest these R9s are already busting, and genuinely I think there's gonna be an extended repair program eventually issued like there were for the 2011 MacBooks.

    So based on both the description of the issue and the widespread problems already surfacing, I'd firmly say it's hardware.
  4. AdiosVista thread starter macrumors 6502

    Sep 10, 2008
    Any specific articles you can point me toward? I'd like to compare my crash logs with others who have had similar experiences.
  5. keysofanxiety macrumors G3


    Nov 23, 2011
    Not to hand, though there are plenty of threads on MR about heat issues & throttling with the 5Ks, and at least 6 or 7 from what I've seen alone about the graphics cards failing and needing to be serviced by Apple. Search around and there'll be loads.
  6. wetcanvas macrumors regular

    Jan 7, 2014
    what I would do is default back to the 8 gb memory config and see if the freezing stops. I had similar freezing in an older machine and it was faulty memory.

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