Probably this is not news for many, but it works! A thing of beauty. First, I installed OS-X on the SSD on the first Apricorn x2. (PCIe #2) Then, since bootcamp will not install Windows on anything that isn't in "drawer" #1, I installed Win 7 Ultimate on the second SSD while it was temporarily installed in this drawer #1. After all Windows updates, I placed this SSD on the second Apricorn x2. (PCIe #3) Turned on the machine and it booted up right into Windows. Of course, option key can give you the choice to boot into OS-X as usual. SSDs are Samsungs 840 Pro. Machine is Mac Pro 5,1 (2010) and the W3690 at 3.46GHz rips. For my standards, this machine is now very fast .