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iMac does not boot ends in white screen and restarts

Hello people

I'm working on a friends iMac (iMac 12,2, Quad-core i7 3,4GHz) that does not start. The loading screen starts and loads up to about 80% then it all goes white for a while and then it restarts.

I've already tried different things:

  • Installing the hard-drive in another mac: starts perfectly fine
  • Installing another hard-drive in this broken mac: same problem as before.
  • Resetting PRAM NVRAM reset: no result
  • opening recovery mode: Recovery mode does not start, apple loading screen appears after loading white screen and restart.
  • Checked some swappable parts (optical drive, Power supply, RAM, Battery): no result.
  • run Apple Hardware Test: no errors
  • run Verbose Mode: screen recording here (dropbox link), last Line is: AppleHDAEngineInput: : performFormatChange (<ptr>, <ptr>, 0)


I hope someone can help me, and that it is not a broken mainboard...


Kind regards


iMac Line (2012 and Later)

Posted on Sep 6, 2019 1:28 AM

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Question marked as Top-ranking reply

Posted on Sep 6, 2019 12:00 PM

Ah, that is helpful then, it's a GPU issue, that is about where it switches from Safe generic Video drivers to special drivers!


Likely Apple has lost this post, but should still clue you in I think, so with the drive connected to a good Mac, preferably same GPU...


See this great post by themachead on how to list the extensions in Safe Mode with System Profiler then compare to the extension folder!


http://discussions.apple.com/thread.jspa?messageID=10161377&#10161377


How To Identify and Disable software extensions on OS X that cause other Apps to crash...


http://www.tempel.org/FindingCrashCausesOnOSX

Similar questions

14 replies
Question marked as Top-ranking reply

Sep 6, 2019 12:00 PM in response to Patrickonzales

Ah, that is helpful then, it's a GPU issue, that is about where it switches from Safe generic Video drivers to special drivers!


Likely Apple has lost this post, but should still clue you in I think, so with the drive connected to a good Mac, preferably same GPU...


See this great post by themachead on how to list the extensions in Safe Mode with System Profiler then compare to the extension folder!


http://discussions.apple.com/thread.jspa?messageID=10161377&#10161377


How To Identify and Disable software extensions on OS X that cause other Apps to crash...


http://www.tempel.org/FindingCrashCausesOnOSX

iMac does not boot ends in white screen and restarts

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