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This is an updated from this question: Buy new Fusion drive I’ve bought the Firecuda 1TB SSHD and cloned the Fusion Drive. When I install the SSHD the mac won’t start. It start to load the OS, but suddently shuts down (power off) Is there any special procedure when replaceing the fusion drive with the firecuda?

Well you can’t clone a Fusion Drive. The best you can do if first break the fusion set so each drive is then visible (the discreet SSD & HDD). You can take the HDD out place the SSHD in it’s place then using a Startech 2.5" SATA to USB adapter connect your old HD to your system so you can then boot up under the recovery partition to gain access to Disk Utility to format to remove the cloned image and reformat the drive, then run the OS installer so it can install the base OS. Don’t worry if this is an older OS. Once done update the OS to the level you are currently running and the needed updates. Only then recover you stuff from your old HDD using the Migration Utility (hint: create a different user account than what you have on your old drive).