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So a few things have been learned regarding the MacPro and NVMe. Booting is fine. Multiple drives on a carrier is not. My MacPro refused to recognize the 4x Hyper 2x carrier with more than one NVMe drive in it. Even in the x16 PCI slot- and I tried both Slot 1 and 2 (there are two x16 slots in the 5,1). So it’s back to holding one drive. I then went and got the cheapest x4 PCI adapter for my 2nd NVMe card and it works fine in the x4 slot. I will get a card that hold two drives at some point and do a final test. For now I have a 1Tb Samsung 970 evo in the Hyper carrier and a 512GB Adata in the StarTech carrier.
The $12 StarTech
The $60 Asus
Slot lanes in a MacPro 5,1
The Mac Pro loded up (4th card is a USB3 PCI card).