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Question: High Sierra install: "An error occurred while verifying firmware"

I have read many other threads on this topic, but none either worked, or seemed to fit my situation.


27" iMac 12,2 (Mid 2011)

Boot ROM Version: IM121.0047.B0A

SMC Version (system): 1.72f1

Non-factory HDD installed when the computer was new


So I think my problem is with the non-original HDD. I replaced the Western Digital 1TB drive with the identical product in a 2TB version. Except it's not identical, and Apple got even with me by not playing well with that drive. Had to install a separate app (HDD Fan Control) to track the drive's cooling needs. EFI Firmware Updates were always a hassle.


I have run diskutil repairdisk, with and without "repairdisk" in and out of recovery mode but it doesn't report any problems in the first place. High Sierra install always runs partway, then does the long "system beep", and seems to quit trying to install a few minutes after that.


I do not have the original HDD from seven years ago, and have not found anything that seems to address my particular situation. I've tried updating firmware, but the only references I've found for that are outdated and don't match what I seem to have already. Any suggestions would be welcome, and thanks very much!

iMac, macOS Sierra (10.12.6), included in post

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Feb 28, 2018 4:55 AM in response to Uni-Cyclone In response to Uni-Cyclone

The replacement drive either does not have the required thermal sensor hardware and the firmware that accompanies it, or its cable is disconnected. Fix those problems by installing a compatible hard disk drive with the required features. Using clever hacks that seek to circumvent that requirement is ill-advised for a variety of reasons including that.

Feb 28, 2018 4:55 AM

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Feb 28, 2018 9:03 PM in response to John Galt In response to John Galt

Thank you John Galt, I suspect you are spot-on with your advice. My "upgraded" HDD was exactly the same brand and model number as the one that came with my iMac, only at 2TB instead of 1. But it wasn't, as the one that came with the iMac was apparently a specialized version for Apple, not available to the general public. There is a heat sensor that was attached to the original drive by adhesive, and it's in place and functioning on the new one, but the new one apparently is missing some hardware and/or firmware that wasn't included on the "general public" version of the same drive.


I am not going to replace my hard drive just to upgrade Mac OS on a 7-year old computer. Lesson learned, don't try to do your own upgrades outside of what Apple recommends (or switch to a PC--yuck)! I'll probably grit my teeth and pay Apple's surcharge to upgrade the Fusion drive in my future iMac...

Feb 28, 2018 9:03 PM

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Question: High Sierra install: "An error occurred while verifying firmware"