So I installed this 6870 on my Mac Pro 3,1 tonight, and I have 3 displays (two 24-inch Gateways and a 42-inch Westinghouse monitor). In the past, I was just using 2 8800GT's. Well, after installing it and trying to use the HDMI port, the Display Port, and one of the DVI ports, I found that, whether I was in windows 7 (64-bit) or Lion 10.7.1, only 2 of the 3 displays will show the desktop, no matter what combination I use. I've tried fiddling in both System Preferences (Lion) and in the Display Settings (Win7) and, no matter what, when I add a 3rd display, 1 of the other 2 displays goes blank. I've tried every combination of DVI x 2, DP, and HDMI, and it happens every time, in both OS's. I will give 1 bazillion Internet Legend Points to anyone who can solve my apparent idiocy.