My friend just got 2 r9 280X's and the crossfire doesn't seem to work. the catalyst recotnizes both gpus and says that crossfire is working but there is not proformance increase between 1 r9 280x and 2 r9 280x's. on of them is from gigabyte and the other one is from msi.
PSU: 1000W, 80bronze
CPU: fx- 8350
Ram: 2 sticks of 4gb
Mobo: ASUS M5A99FX PRo