Depending on the model you have it could be different but from what i saw the most common config I see is 1 DVI port 1HDMI and 1 display port. Depending on your monitors most likely you will need to get adapters to DVI.
You seem to have the same problem as I am having. Maybe you have seen my thread.
The key is the Displayport connection. This needs to either be to a Displayport monitor or have a special adapter.
There are two adapter types to change a Displayport to DVI (or Displayport to HDMI). Passive ($15 - $20) and Active ($100+). You HAVE to have an Active one. You will know it is Active because there will be three connections.
3. DVI (or HDMI)
AMD lists approved dongles, but within that list, for Eyefinity, you have to choose an "Active" one.