Steinberg has released a compatibility update “Yamaha Steinberg Firewire Driver V1.7.5” for the MR816X/CSX:
http://www.steinberg.net/en/support/downloads_hardware/yamaha_steinberg_fw_driver.html
However the note says.
Compatible (with subsequent Yamaha Steinberg Firewire Driver V1.7.5 installation). TOOLS for MR planned
How is this to be interpreted? That the 816s are compatible with Sierra, but still not since a TOOLS update is planned?
EDIT:
Interesting. The newly released driver is version 1.7.5. However, the version installed with TOOLS for MR V1.7.7 also was 1.7.5! The old v1.7.5 wasn’t compatible with Sierra, but the new v1.7.5 is. Have Steinberg mixed up the version numbers?
The plot thickens, Watson, as our old friend mr. Holmes would have said.