Out of the box the USB 3.0 may not work at all on MSI 970. I searched far and wide, until I found someone using same motherboard on linuxmint distro with same problem. They had a fix but it had a con, however since I did it there were no issues whatsoever so this fix works even better than I thought.
- from a terminal session enter the following commands: sudo gedit /etc/default/grub
- change the line GRUB_CMDLINE_LINUX="" to GRUB_CMDLINE_LINUX="iommu=soft"
- save this changed file and EXIT the terminal session.
- start another terminal session and enter the following command:
- sudo update-grub
- EXIT this terminal session and reboot