The problem I mentioned here:
was solved by the last Crimson Edition 16.3.1 Hotfix driver
But here are some strange results:
With 6bit panel dithering kicks in (you can see it because it turns off for split of second when using catalyst control center) and the screen looks EXCELENT!
But with 8bit panel is dithering disabled and it looks WORSE than on 6bit screen with dithering on!!!
How to turn on dithering with build-in 8bit LCD panel?