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I have a 2013 A1419 27" iMac (i5/3.4Ghz) which had a cracked display. I got a replacement in, but it took me a couple of days to realize I also had to move the heat sensor that was on the old display. Prior to that I had been trying everything to get it working properly and the fan not spinning up to full speed with every boot! One thing I tried was to reformat the Blade SSD attached to the back of the logic board, but now that I know the issue wasn’t the SSD drive (yes, I purchases the OWC Inline heat sensor) or the installation of same, I need to format the blade drive on the logic board back to “unformatted” which is what its designation was before. I’ve tried Disk Utility, Drive Genius and I’ve looked at Terminal commands, but do not find a command or item that does what I need. I think possible “writing zeros” in Drive Genius might, but not sure, any “unformatted” formatting thoughts? Thanks, JoeL ATL
First you’ll need to create a OS installer drive (USB Thumb drive) following this guide: How to create a bootable macOS Sierra installer drive. Make sure your HD is fully backed up before proceeding. Booting up with the Installer will allow you to delete any partitions on the SSD using Disk Utility. We don’t need to worry about having a GUID partition table. At this point you’ll need to open a terminal session as you’ll need to work with CoreStorage at the UNIX command line to bind the two drives together. Here is the guide to recreate the Fusion Drive: How to make your own Fusion Drive. Now before you do this if you have the original SSD that was part of your original Fusion Drive then go ahead. If you put in your own Apple custom SSD and its larger than 128 GB you might want to leave the system as a two independent drives which will give you the better performance. In the end its what works for you! Some people like the flat logical volume a Fusion Drive offers.
