I have a 6990 and currently have 5 screens attached. If I purchase another 6990 will it let me attach another 5, so that I have a 10 screen desktop display? Could I do this in Crossfire or would they have to be separate?
Yes, up to a total of 24 screens is possible. http://www.youtube.com/watch?v=N6Vf8R_gOec
CrossFire requires that all screens are connected to the primary card, so has to remain disabled.