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iMac Intel 27" EMC 2309 (Late 2009, Core 2 Duo 3.06 or 3.33 GHz) ID iMac10,1, EMC 2374 (Late 2009, Core i5 2.66 GHz or Core i7 2.8 GHz) ID iMac11,1

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iMac not booting unless in safe mode. Hardware cause?

Hi there!

The iMac of my wife won't boot anymore unless in safe mode.

She didn't install anything, she says, which I tend to believe as she is a very conservative user. I'm not sure she even would get through an installation process by herself.

Some weeks ago, she reported a clicking sound out of the machine, perhaps a fan (her guess). This clicking sound disappeared though some days later. As the system is running off an internal SSD that I have changed the SuperDrive for some years ago, it can't be the drive.

On Friday, while working on her Word document, the Mac froze, only the mouse cursor responded. She restarted but the Mac booted only half way through.

In safe mode it boots.

Things I checked:

  • PRAM and SMC reset
  • Disk Utility test
  • SMART Utility test

All fine.

As usual suspect seems to be the graphic card, I removed /System/Library/Extensions/ATI4800Controller.kext. (It's got the 4850 512GB card.)

That didn't change anything. There were also no discernible graphic problems before.

So now I have two questions:

1) Does this rule out the graphics card as the cause of the problem?

2) How can I find out which other hardware part can cause it? The later Diagnose Tool doesn't seem to exist on the Late 2009 iMac. Is it worth to search for the original DVDs to find the hardware test?

Ответ на этот вопрос У меня та же проблема

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Well… Safe Mode uses the firmware driver which uses the Intel chips Iris graphics engine. Which explains why it works and when you run via the OS the AMD (ATI) Radeon MXM graphics board doesn’t.

During the boot-up POST process SMC can fail to complete as it doesn’t get the expected return from the graphics board. Hence the system won’t boot up.

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Thank you! So even if I remove the kext, it tries do address the graphic card?

I read elsewhere, that with removed kext it will finish to boot and run from the Intel chips Iris graphics engine - even in normal mode. That would speak for the graphics card as the definitive culprit. In my case, it didn’t finish the booting process, though. So I’m still not sure.

If it is plausible that the graphics card is involved I would try to bake it in the oven.

If not, not, obviously.


@frantisekhavel - The driver (kext) is loaded after the POST process when the OS is then loaded.

The issue is what failed within the board. If the POST completes, that would force the Iris graphics to kick in.


Thanks a lot, so I will give it a shot. not much to lose on a 14 year old device, anyway. It was a great Mac ;-)

All the best!



I gave it a shot, baked the card – and it worked!

Unbelievable! Thanks!


@frantisekhavel - happy it worked! Don’t forget to accept the answer.


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Frantisek Havel будет вечно благодарен.
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