Question: When I install ATI HD6670, HD6570, and HD6450 on A75/A55 series motherboards, there is no display output from VGA card. What can I do?(9/1/2011) Answer: Please update latest BIOS form our website.
Download link: https://www.asrock.com/support/download.asp
Or, enter BIOS > North Bridge Configuration, and set [Dual Graphics] to [Disabled].