I got my Eyefinity working on 3x 22" (1680x1050 res screens) with Windows 8 x64 and 2x Radeon HD 6870 running on crossfire. I needed one active DP adapter for that. For example Battlefield 3 and Need For Speed Shift works nicely.
...But, i tried out Need For Speed Prostreet few days ago, and some weird issues came up. -I searched a load of forums for increasing resolution and I got that problem solved...but still:
-Major problem is that the game stretches graphics to match 5040*1050 resolution. BUT displays on only one screen. (which is the selected "preferred display" at Vision Engine CC) other screens go no-signal. After exiting the game everything is fine again. I tried everything on Windows 7 too, with excatly same behavour.
-Is there something with new catalyst drivers or what is this. I can't remember seeing the whole "preferred display" setting before (I maybe wrong, but still...)
Catalyst Version 13.4
-Haven't tried out roll back catalyst yet, because everything else seems to work fine.