This iMac was my father's and began having this issue last summer. It will simply power off completely at random - sometimes being able to be powered back on immediately, sometimes not turning on for an hour. This problem persisted for months and grew more frequent until it was happening several times a day.

Rather than try to deal with it over long distance, I had him buy a new iMac and took the old one with me to NYC. Took to Apple, who found nothing wrong.

I reformatted the drive, did a new install and step up with new software in a completely new environment - I did NOT restore from any user or backup. Within a week the Mac started shutting off again.

I brought it to Apple again. They kept the machine this time and ran diagnostic over days but could not get it to repeat shut down in their possession and insisted it was a software issue. We rebuilt the machine once more and tried again. This time it worked for a few months before starting to shut down occasionally again. At first just every few days, then nearly daily (oddly often around the same time in the afternoon), and then multiple times a day.

I brought back to Apple once more and eventually spoke on the phone with a master tech somewhere in the Midwest who also thought the "Geniuses" must be missing something and gave them more stressful test to try. Again, they can't get the machine to replicate the problem.

• This machine has been rebuilt several times.
• This machine has been in two completely different environments, with different sets of software from different sources.
• I have swapped power cords. I have tried different surge protectors and outlets.

I am at a loss and Apple will not tell me anything is wrong to replace.

Except for the shutting off, this still remains one of the fastest Macs I've used from probably 15 different 27" models from 2010 - late 2015.

Any suggestions? Thank you very much.

⟐ Commented December 02, 2025 at 16:00 MST

I used to use SM951 AHCI in Mac Pro 5.1, 6.1, all Retina and Air 2013-2015 but what about NVMe once? Have anyone tried?

⟐ Commented November 28, 2025 at 13:00 MST

So, I need a new card.

• Are all MXM 3.0 B cards compatible or does the card need Apple firmware?
• Would a 6970M card for a Dell Alienware laptop or another card with the same chip as one of the iMac 2011 models work?
• Where can I get a card that works? (<400$)

I've see a lot of questions and answers that dance around these questions but none that actually answers them specifically so ANY help will be greatly appreciated.

• ''Are all MXM 3.0 B cards compatible or does the card need Apple firmware?"
• "Would a 6970M card for a Dell Alienware laptop or another card with the same chip as one of the iMac 2011 models work?'

I found out Apple uses special firmware and for a card to work it needs an EFI flash with Apple firmware.

A card without Apple firmware will simply result in a black screen.

A friend of mine did suggest I could remove the BIOS/EFI-chip from the original board and reflow it onto a cheaper card - but that will probably be too complicated for a lot of people and I already had a new card on the way.

Cards that already have Apple firmware (pulled from iMacs) are interchangeable though - I upgraded from the 1GB 6970M to the 2GB version.

• "Where can I get a card that works? (<400$)"

You can get a working card on Ebay or Aliexpress - any MXM 3.0 card pulled from an iMac should be fine. I paid ~300$.

Lastly, as @mayer pointed out, if you have an iMac 27" Mid 2011 with issues, the GPU is most likely the cause and Apple will fix it if it's no older than four years, because it's a recognized issue.

Apple refused to fix this one because it was sold in 2011 but if you want to fight Apple, maybe that'll work too - I chose to fix it myself instead.

⟐ Commented July 31, 2024 at 10:24 MST

After that the iMac doesn't boot properly. It does the chime sound, then the apple logo with indicator and then just goes to a white screen. The keyboard doesn't work as caps-lock light wont come on.

I have tried the following:

• RAM reset (Cmd+Opt+P+R)
• SMC reset (unplugged power source for 2-3 hrs, held down power button for 10 sec)
• Removed ram cards and powered up, it did the SOS beep with 5 second intervals, so I'm guessing logic board is fine
• Holding down Option key during startup brings up the disk selector (I have 2 partitions one with Lion and one with Mountain Lion) neither boots up.
• Tried booting from an external Mountain Lion Install USB drive, it shows up in Disk Selector, am able to select it, but then it stops at white screen
• Ran a thorough Apple Hardware Test off the internet through ethernet cable, took 1:45 hours and it showed no errors
• Tried to run through Mountain Lion Recovery Disk, same white screen
• Entered sIngle user mode (Cmd+S) and ran fsck -fy on boot disk, it gave a few minor errors, so I repeated fsck -fy a few times until it no longer gave errors, still doesn't get past white screen. I'm able to browse the HDD in single user mode using the shell. Then did "exit" and also "reboot" commands, both ended in white screen.

I've looked around and found several guides dealing with this exact problem, but as you can see from the elaborate list above, none of those remedies have worked for me.

Any help is greatly appreciated, I'm on a tight deadline to finish this animation project and this is the only machine I have access to at the moment.

I don't have Apple care nor warranty and there's no Apple store/Genius Bar nearby.

⟐ Commented March 12, 2024 at 14:44 MST

I installed 64GB of RAM into my iMac 4 x 16GB

After the upgrade the system fails to boot. I can hear the hard drive, however the screen is off, with the old RAM the iMac works as expected.

I have verified that the RAM is compatible and should work with my iMac.

Any solution to get the iMac to work with the new RAM?

⟐ Commented April 19, 2024 at 12:48 MST

This is the SSD that I ordered: http://www.newegg.com/Product/Product.as...

I am currently booting off that SSD, which is connected via USB 2.0, and I believe that it's being bottlenecked by USB 2.0.

⟐ Commented July 18, 2021 at 10:30 MST

⟐ Answered April 09, 2025 at 1:30 MST

⟐ Answer edited December 14, 2021 at 12:22 MST

Thanks! -Zach

⟐ Commented June 21, 2024 at 21:01 MST

⟐ Commented May 24, 2020 at 20:56 MST

So... The New Intel CPU 8700K is now available!

I just want know can I replace my i5 7600k to the new i7 8700k?

Is it possible to upgrade?

Thank You So Much

⟐ Answered May 30, 2023 at 9:28 MST

But the main point I need the OS & software run it faster instead of need a largest storage. Just wondering is easy to change it to SSD if the specs is Fusion Drive not. Or get the SSD specs is better, so if need to upgrade in future is still feasible.

⟐ Answer edited April 20, 2024 at 14:32 MST

⟐ Commented December 06, 2025 at 5:34 MST

I have already replaced the power supply with the same result. I also have tried unplugging both the HDD and the SSD and it still was restarting. I have tried switching out the RAM from another iMac and it still restarts.

When it restarts, it randomly shuts off and then boots again, sometimes over and over.

I have already taken it to an authorized Apple tech, and they told me they could never get it to reboot... the closet Apple Store is over 3 hours away so I am trying to troubleshoot this myself.

Any ideas on what I can try next? Thanks for your help!

⟐ Commented December 25, 2024 at 14:33 MST

thanks for answer

⟐ Commented February 07, 2023 at 6:14 MST

But while trying to close the iMac screen, all adhesives lined up, I connected the display's power cable and ribbon cable. Mistakenly, I lifted the display while trying to align bottom and ouch....the ribbon cable (vsync cable??) pulled out from its connector argh.....

I connected it back and closed the iMac. When I powered up there was a green vertical line (which was gone after a min) and the gray/black thick stripe about 1.5inch wide. This stripe stays all the time from boot to shutdown.

Tried SMC reset, PRAM reset... no luck.

I doubt the ribbon cable damage (is it vsync cable)...now I'm skeptical to reopen to play around without knowing what could be the issue.

Many questions on my mind....did I damage the display? Is the ribbon cable replaceable (I tried googling for spare part couldn't find a proper lead)?

Any help would be much appreciated thanks.

Finally fixed the expensive mistake :)

Had a local shop fix my system in Dubai

Also the iFixit adhesive strips and the removal tool are a must have!

[linked product missing or disabled: IF173-005]

⟐ Answered March 19, 2026 at 12:01 MST

⟐ Commented February 18, 2023 at 12:40 MST

Can I swap out the original wifi card for an Intel 7260 card that gets 802.11ac? The connectors look the same but the intel card has Bluetooth on it as well, would this be an issue?

I run nothing but windows on my imac now.

It sure would be nice to get gigabit wireless as I am upgrading to an SSD hard drive.

Thanks in advance!

⟐ Answer edited August 03, 2024 at 3:27 MST

Is that possible and has anyone already done it?

⟐ Answered September 19, 2021 at 3:19 MST

Need some help please! I woke up one morning recently to find my iMac was dead to any input. It was working fine the night before, I didn't shut down and just let it go to sleep on it's own. There is zero response when the power button is pressed, no boot chime, no screen response, no fans/hard drives spin… nothing.

What I've tried so far:

• Different power sockets, different power lead
• Reset SMC
• Replaced PRAM battery
• Replaced iMac power supply
• Removed graphics card

There is only one diagnostic led lit on the logic board (labelled LED601) when the iMac is plugged in:

There are 4 LEDs in total and it's the led furthest from the board edge that lights up. Strangely the service manual for this model seems to list the LEDS in an opposite order to my board:

I assume the LED that is lit up must be LED 1? ( indicating that trickle voltage from the power supply has been detected by the logic board).

Does this mean that it's most likely a logic board fail? why would the logic board suddenly fail overnight when iMac was sleeping?

⟐ Commented August 12, 2023 at 5:54 MST