Woah 
Between v11.1 and v12.0 i'm getting a huge hash drop. With 11.1 i'm getting ~205H on my R9 290. When I just fired up the v12.0 i'm only getting ~69-~75H. Am I missing something? I just checked 11.1 again and it's fine so it is definitely something in 12.0 :S..hmm.
Between v11.1 and v12.0 i'm getting a huge hash drop. With 11.1 i'm getting ~205H on my R9 290. When I just fired up the v12.0 i'm only getting ~69-~75H. Am I missing something? I just checked 11.1 again and it's fine so it is definitely something in 12.0 :S..hmm.Well maybe you're missing some overclocking stuff here? Have you checked the start file and the driver configuration?
I guess something is wrong with your configuration of inner features of miner, such as undervolting using miner directly. Or maybe you're over-clocking too much which is hard to handle for the newer version because of its optimization.
Nope, not overclocking or undervolting at all. Everything is stock. Lowering the intensity does help but it is still much slower than 11.x without any extra settings.
Your 11.1 config is not ok. 200h/s is really low for a 290, it should be 260-300h/s with stock bios, 350+h/s with 390x bios. 290x @ 1075mhz do 400h/s.
Have you tried using DDU to remove Radeon drivers and installing 15.12? Most problems are fixed by removing and installing drivers. Have you checked the temperatures? Have you check the voltages?
I have lots of 290/290x working 24/7 with v11.1 and now v12.0. v12.0 does not like undervolting the GPU and some cards needed to be slowed down from 1100MHz to 1075MHz.