I got crossfire extension v1.4 from here.http://www.ati-forum.de/allgemein/downloads/tools/1376-ati-crossfire-xtension-v1-4/ Using this software and the built in Crysis profile, I am getting 30 - 70 fps, depending on the area I am flying over. I know crossfire is working because both GPUs are reaching about 68 degrees. Here is my system. AMD PHENOM II X6 1090T (3.20GHz/9MB CACHE/AM3/) - BLACK EDITIONASUS® M4A89TD PRO/USB3 : DDR3, USB 3.0, SATA 6.0Gb/s, CrossFireX8GB KINGSTON HYPER-X GENESIS DUAL-DDR3 1600MHzx2 1GB AMD RADEON™ HD 6870 PCI EXPRESS Good luck.