I play this game called Darkfall Online which is a DX9 game. The refresh rate works fine for Nvidia cards (I tried with my old 470) but it just wont work no matter what I do on my AMD gpu. I tried with both my 7990 and a friends R9 270x. I had the latest version of the crimson drivers so I reverted back to 15.11.1.
I tried unplugging my second screen.
I also tried CRU to no effect.