Model A1419 / EMC 2806 / Late 2014 or Mid 2015. 3.3 or 3.5 GHz Core i5 or 4.0 GHz Core i7 (ID iMac15,1); EMC 2834 late 2015 / 3.3 or 3.5 GHz Core i5 or 4.0 GHz Core i7 (iMac17,1) All with Retina 5K displays

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Confused about custom firmware

Hi All.

Can someone pls help clarify the firmware situation for me pls? I have a 27 inch 5K late 2014 iMac and the 3TB fusion drive has failed.

I have managed to determine that the conventional drive is the part at fault and I want to change it, but I am reading about custom firmware's. Is this true? or am I able to just swap out for a new "off the shelf" Western Digital 3TB drive?

If it is true about the firmware how do I get a compatible drive and how do i install the custom firmware.

If I buy an identical drive to the 3TB Seagate drive, Can i just swap over the circuit board from the dead drive? Would that contain the custom firmware?

Thank you for any advise you can offer.

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When you use a non custom firmware HDD on iMac the HDD fan turns always high.

To bypass that you can use OWC in-line sensor adapter sensor cable or MacFanControl software.

Swapping the board could work if they are the same exact model (never done it so not a 100% sure it will work here)

In addition to all of this you'll need to recreate the Fusion Drive volume. On YouTube you'll find a few vids on how to do it (English or French ), since putting in a new drive will not automatically restore your Fusion Drive.

I don't know a method to flash your HDD to be like Apple's custom one.

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@soros is correct here you'll need to offset the lack of internal sensor

I strongly recommend using the OWC in-line sensor cable as its much better than the software over-ride.

Apple contracted the HD companies to make a custom drive for them. In truth as you've already figured out the drives firmware was altered so the internal thermal sensor within the HD was compatible with Apples SMC service. Sadly Apple is not allowing the HD companies from selling the compatible drives directly so if you get the off the shelf drive you'll have a problem without the OWC adapter.

As to swapping out the drives logic board. It's chancy if it would work. You would require the exact same drive to even attempt it. Most people are looking on getting more storage or a faster drive than what Apple used for a HD so I've not tried doing this my self either.


@danj Thanks for your advice on this. I think i am going to do exactly that. I am not interested in increasing the storage capacity but I would like the same so my TM can restore to as it was before the drive failed.

Also buying a fairly decent HDD, the OWC in-line sensor and the ifixit kit (with the pizza slicer) saves me around £70. Which doesn't sound much but for my family its a big deal. Not to mention the value of experience.

Thanks again. :)


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