Download AMDGPU-Pro Driver Version 16.30 released by AMD.
The basics of the install:
1. download amdgpu-pro_16.30.3-306809.tar.xz
2. extract the compressed file to your home folder or somewhere.
3. goto that folder and now run the installation script "sudo ./amdgpu-pro-install"
AMD's page support.amd.com/en-us/kb-articles/Pages/AMD-Radeon-GPU-PRO-Linux-Beta-Driver%E2%80%93Release-Notes.aspx
And here is the direct link to the compressed file:https://www2.ati.com/drivers/linux/amdgpu-pro_16.30.3-306809.tar.xz
NOTE: You have to extract the compressed file and then run the script to install the driver to make opencl devices detectable (for ethminer, oclhashcat, etc.)
I am using 6 - RX 480 (4GB model ) in Ubuntu 16.04 LTS
Stock settings. I believe the ram is at 7000mhz vs 8000 mhz in 8GB version.
Ubuntu 16.04 LTS
Driver is 16.30 for Linux
2 - XFX 4gb rx 480
4 - Sapphire 4gb rx 480
Doing about 134-139 mh/s. I'd say its doing about 22.5 or 23mh/s in Ubuntu 16.04 in stock mode.
Next up is finding out how to overclock/undervolt GPUs in Ubuntu 16.04 with atitweak or something else (amdconfig/aticonfig do not work anymore unless I need to install the SDK.. we shall see.)