I recently purchased three NUC7i7BNH. I used http://www.samsung.com/semiconductor/minisite/ssd/download/tools/ Samsung's Data Migration Software to clone a Samsung SATA SSD to three Samsung M.2 960 EVO SSDs. For simplicity I will refer to the NUCs as NUC1, NUC2, and NUC3.
I put SATA SSD in NUC1 and cloned data from SATA SSD to each M.2 SSD (all three). I then remove SATA SSD from NUC1.
I can put any of the three M.2 SSDs in NUC2 or NUC3 and everything works.
Any of the three M.2 SSDs in NUC1 and NUC1 gives me that INACCESSIBLE_BOOT_DEVICE.
If I put SATA SSD back into NUC1 and boot to SATA SSD (Windows 10) then go to Disk Management I see this any of the three M.2 SSDs:
The drives work and the NUC1 appears to work with M.2 (except for signature collision).
Here is pictures of BIOS with only M.2 SSD (BIOS version is 4/13/2018 0063):
Any ideas? I opened a support request with Intel and sent them this data.
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First, please go to BIOS > Devices > Sata. Make sure the the units have the same Chipset SATA Mode chosen and the same configuration.
Also, do you have the same BIOS version in all the units?
Except for the BIOS factor, boot devica failure (the boot device driver might fail to initialize the boot device during I/O system initialization), file system initialization failed, and incompatible disk hardware are also possible causes for the https://www.disk-partition.com/windows-10/windows-10-inaccessiable-boot-device-5740i.html inaccessible boot device error.
If you don't feel trouble, clean install is recommended.