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Question: iMac Won't fully Boot (black screen spinning)

I went to help a friend with an issue she was having with her:

Mid 2011 27" iMac 4GB i5 running iOS 10.12.3 (Sierra)

She wanted to try Photoshop so I downloaded the trial and the computer completely and totally froze on install.

As such I had to force restart the machine (something I never like doing while installing).

Since then the computer will not fully restart... It goes through this same cycle every time:

1: Chimes

2: Grey screen with Apple Logo

3: Dark progress bar (for startup) freezes around the 3/4 mark

4: Screen flickers Black

5: Grey screen come back but then dims to dark grey (like it would before it would sleep)

6: Screen goes totally black with spinning wheel (not the beach ball but the hollow spinning grey wheel) flicking on and off. the cursor is also visible at times on screen in the top left corner...

7: Never moves beyond that point.

I have tried the following:

A: Reset SMC and PRAM

B: Command - R reinstalled Sierra

C: Ran "first aid" on HD (HD passed)

Any suggestions on how to fix this quickly would be greatly appreciated.

iMac, macOS Sierra (10.12.3), mid 2011 27" iMac 2.7Ghz / 4GB

Posted on


Mar 2, 2017 5:20 PM in response to sConvey In response to sConvey


A Safe Mode boot deletes system caches that might help ..

To start up in safe mode:

  1. Start or restart your Mac, then immediately press and hold the Shift key. The white Apple logo appears on your display. If you don't see the Apple logo, learn what to do.
  2. Release the shift key when you see the login window. If your startup disk is encrypted with FileVault, you might be asked to log in twice: once to unlock the startup disk, and again to log in to the Finder.

To leave safe mode, restart your Mac without pressing any keys during startup.

Use safe mode to isolate issues with your Mac - Apple Support

Mar 2, 2017 5:20 PM

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Mar 2, 2017 6:22 PM in response to Carolyn Samit In response to Carolyn Samit

Hey there, Thanks for the suggestion but "Safe Mode" does not work either (same result as normal reboot).

I did start it up in Verbose mode and these are the lines that are blinking (in the top left corner)

I assume this has something to do with why the computer is currently hanging...

IOConsoleUsers: time(0) 0->0, lin 0, llk 1,
IOConsoleUsers: gIOScreenLockState 3, hs 0, bs 0 now 0 sm 0x0

Mar 2, 2017 6:22 PM

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Mar 16, 2017 7:18 PM in response to sConvey In response to sConvey

This is happening to me during last two months several times. One way that I found to solve temporarily it's reinstalling IOS, using cmd+R command during booting. This will solve the issue for a couple of days or a week in best case. I think the problem is related with video card. Let you know any progress.

Note: it is possible that you have to try CMD+R command several times to get the recovery options.

Mar 16, 2017 7:18 PM

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Mar 16, 2017 8:35 PM in response to sConvey In response to sConvey

I agreed with the answer that I'm copying below. It is a problem with the video card AMD Radeon HD 6970M. The answer from apple is the replacement. Apple open a program to replace the cards in iMac that applies but it is ended. My iMac serial number is part of the affected devices, ends with xxxxxxxDHJQ.

There is nothing else to do.

Re: IMAC 27 Inch (Mid 2011) keeps restarting halfway through booting up

Mar 16, 2017 8:35 PM

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Question: iMac Won't fully Boot (black screen spinning)