I've got 740 Radeon with to outs for monitors. Do you know how can i configure second out to work ?
Had the same problems with a Radeon x1400 in Ubuntu. Finally, I was able to activate the external out with xrandr. In Ubuntu, it can easily be installed if it isn't already.
But as mentioned, you need to give more information: Which OS? What "outs", vga, dvi ?