@Diggs The whole problem with that system was not because it was"Optane" memory. Optane is simply a fast kind of chip. HOW it is interfaced is the issue. That system was set up with a 16GB buffer on the SATA drive. The buffer has to be turned on or off in BIOS or Windows and can only be done if the drive is present. Chances are once you disabled the buffer both of the drives mentioned in your OP would have worked. A buffer is yet a THIRD option for M.2 slots and only works if the chipset supports that function. Most don't.