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Level 1

15 points

5k iMac reboots on it's own after installing 10.11.4

Hi,

I installed 10.11.4 on March 24 (I believe), and since that day my iMac has been unstable. It reboots on it's own, like a kernel panic but never logging a kernel panic. This reboot doesn't seem to be triggered by software I run, as I've been removing things to try to isolate the problem.

Yesterday Apple Support had me reinstall the os via cmd-r boot option, and that did not solve the problem... it just ate up an hour of my time.

Any suggestions? My iMac went from super stable to super unstable; it's worse than my Windows gaming pc for stability now.

iMac (Retina 5K, 27-inch, Late 2015), OS X El Capitan (10.11.4), 32GB ram

Posted on Mar 29, 2016 4:57 AM

107 replies

nicklear

Level 1

4 points

Oct 12, 2016 11:24 PM in response to GNW3

I posted in the other thread for this topic, but for those reading this thread, I had the same problem with my refurb late 2015 27" which came with 10.11.4 and installing Sierra fixed the problem for me. And it seems to have updated the firmware it is now IM171.0105.B09 so I guess Apple did figure out how to fix the problem without replacing hardware.

Dec 5, 2016 3:51 PM in response to Terry Murphy

Joining others who report the issue appears to be resolved in sierra - finally. The unexpected restarts are gone. I have not replaced my iMac. It remains the same machine I purchased late 2015 which ran perfectly until 10.11.4

I suspect it was a bug introduced in 10.11.4 in relation to power management. The skylake processors in particular were still fairly new at the time. Seems like a common thread that the high end build to order late 2015 i7 iMacs were reported frequently with this issue. All Apple needed to do was set up a such a machine with 10.11.4 or later running in a lab - just boot it up and let it sit. Come back in a week (the problem occurs whether you are using the machine or not) and see when the previous shutdown occurred - because it would never run for more than a week without an unexpected restart on any version of 10.11 from 10.11.4 onwards.

5k iMac reboots on it's own after installing 10.11.4