2011 IMac is white screening at bootup, Recovery and Internet Recovery

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2011 IMac is white screening at bootup, Recovery and Internet Recovery

I have an old iMac I’ve been given by a friend, who has replaced the old HDD with an SSD. After booting it up, I am unable to find a way past the white screen of death.

Regular bootup gives me the chime, apple logo, progress bar and then a fade to WSOD, the Mac then reboots after a short while and does the same thing.

Booting into recovery mode gives me an apple logo, a much longer progress bar as expected, and then WSOD after the bar has got to just over halfway.

Booting into Internet Recovery gives me the normal internet recovery process (choose your WiFi, spinning globe, progress bar, countdown) all working fine, then apple logo plus progress bar, and then WSOD.

I have tried the following:

PRAM reset - this got me the boot chime back, which was previously missing.

Boot into safe mode, doesn’t seem to make a difference.

Booting into target disk mode, works fine.

Diagnostic mode reported a single error, which is the code for missing thermal sensor on the HDD. I know that these are integrated into the original HDDs and so this makes sense, as the aftermarket one that you use with SSD replacements isn’t present. This is also why the fans are at full throttle all the time.

I’ve taken the SSD out and plugged it into my MacBook, and it seems to work fine and have the correct folder structure for a bootup disk. I can also see the documents etc from when my friend was using it previously.

Booting while pressing Option shows me the SSD as a bootable drive, but does not show a recovery partition.

Any help as to what is wrong? the best I can surmise from googling is a faulty GPU, but it seems odd that this only seems to kick in after all the progress bars or internet recovery/diagnostics windows are finished. Do these macs switch to the AMD gpus for the recovery interface?

I also suspect that the SSD doesn’t have a recovery partition, but this doesn’t explain why internet recovery also goes to WSOD.

Any help greatly appreciated.

Thanks

Posted on Mar 30, 2025 5:33 AM

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Answer 1

Allan Jones

Level 9

73,916 points

Mar 30, 2025 9:32 AM in response to CharlieB777

Diagnostic mode reported a single error, which is the code for missing thermal sensor on the HDD. I know that these are integrated into the original HDDs and so this makes sense, as the aftermarket one that you use with SSD replacements isn’t present. This is also why the fans are at full throttle all the time.

Indeed. The fact that your friend ignored the need for a special thermal sensor cable (see this) could indicate other install issues with the SSD.

Do you know the MAKE and specs of the SSD. Not all SATA SSDs are Mac-friendly. Most senior member here recommend either the Crucial MX series (not the old BX), or SSDs from OWC. The 2011 iMac was the first to have the faster 6GB SATA drive bus, so that drive spec is the one to use.

Is this a 21.5 or 27-inch model? The 27's in 2011 seem to suffer a higher rate of GPU failures that the 21.5s. Used/pulled GPU assemblies for that model have all but dried up and, if found, can cost more than all the other parts in your used iMac are worth if you broke it down and sold them separately .

That iMac model was the last shipped with optical install/restore disks. Depending on its macOS version, it may not have a recovery partition. I do not recall seeing a recovery option the the Startup Manager; use the key combos in this Apple article instead:

How to start up from macOS Recovery - Apple Support

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Answer 2

CharlieB777 Author

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Mar 30, 2025 9:50 AM in response to Allan Jones

Hi, thanks for the reply. This is a 27” 2011 iMac.

I plan to try with another SSD that I know works, as I do also own a 21.5” iMac running high sierra. That one does have a recovery partition, which is what led me to believe this one should also.

I have just tried to boot from an external USB running OSX Lion (that I have tested to work on the 21.5” iMac) and that does exactly the same thing, completing all the steps before going to WSOD at the point that it should display the recovery options window. Do external USB boots also try and use the recovery partition? I’m trying to isolate the GPU as the problem before I start hunting down a replacement.

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Answer 3

Allan Jones

Level 9

73,916 points

Mar 30, 2025 10:09 AM in response to CharlieB777

I’m trying to isolate the GPU as the problem before I start hunting down a replacement.

Good plan. One way to check is with an external monitor. If an external monitor shows a proper image, the issue is in the display or its cabling. If not, the issue lies deeper, likely the GPU.

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Answer 4

CharlieB777 Author

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Mar 30, 2025 10:17 AM in response to Allan Jones

Good advice thanks. I feel like the display itself is fine, given how well it shows all the internet recovery setup bits etc.

really, I’m just desperately hoping someone has an idea that isn’t a failed GPU, because as you say, that’s probably a death sentence for the Mac.

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2011 IMac is white screening at bootup, Recovery and Internet Recovery