Hi, I am running a Ubuntu 14.04 mining rig with a mix of R9 280 and HD7970 GPUs.
I thaught I’d gradually upgrade it to newer GPUs: can I add a RX 480 to the mix?
I figure t hat I need to upgrade to Ubuntu 16.04 to support the RX 480, but will the drivers be compatible with my old cards?
Don’t think so, my 7850 wouldn’t work with the newer AMDGPU pro driver. But it works in Windows.
Ok, you’re right, the older cards are not on the list of supported devices for AMDGPU pro 
is it somehow possible to install both the old fglrx and the new AMDGPU side by side in a linux environment? I am very hesitant to switch to Windows…
Join the dark side 
Haha 
I am still interested in a Linux solution, but lets say I want to join the dark side: Whats the cheapest way of getting a legal copy of Windows?
I purchased PRO keys from https://www.kinguin.net for about ~28 EUR with buyer protection.
I bought 3 keys the last few weeks for my Zcash rigs and then installed Ubuntu 16.04 after Windows 10 (dual boot with Windows boot manager on one SSD).
That’s not too bad, thanks! I’ll use that as a last resort
Still, is there anybody out there who uses old and new AMD gpus side by side in Linux?
You can try Windows for free for 30 days… by then a solution might be available