Thanks nerdralph
I am not seeing much that you did in your blog that I have not tried, other than using the --px option when installing. I wish you gave a little more detail, like every step, with commands (like I did in my first post). Then I could duplicate exactly what you did and it may work for me.
I am beginning to come to the conclusion that these cards just don't run correctly with the current linux drivers, and I will need to stick to windows.
It is really strange that I can run an almost identical card just fine (powercolor red devil rx580 8gb works just fine). But the msi rx580 8gb does not.
I prefer not to duplicate the information in the AMDGPU-Pro release notes, and just link to it instead. If you haven't tried upgrading your kernel, I'd do that too. Renaud posted in the comments with a nice script for downloading and installing updated kernels.
http://nerdralph.blogspot.ca/2017/03/amdgpu-pro-1660-on-ubuntu-kernel-4105.htmlFor some debugging tips, see what you get when you run "dmesg | grep amdgpu" and "dmesg | grep BIOS".
rocm-smi is also very helpful for checking on your cards.