Plug it into the top card. Either card will work, but the top is preferred. Btw, using HDMI you may have to go into CCC and adjust the overscan to get a full width screen. It's a bug that sometimes occurs. Doesn't seem to happen with DVI.
Plug it into the top card. Either card will work, but the top is preferred. Btw, using HDMI you may have to go into CCC and adjust the overscan to get a full width screen. It's a bug that sometimes occurs. Doesn't seem to happen with DVI.
I realize you came on here for help, but you're the first person I've run across who has actually tried to Crossfire 7990's. Tom's Hardware did a 7990 Crossfire review that is mandatory to read and will be of help if you run into problems with heat and GPU throttling, which you will. http://www.tomshardware.com/reviews/radeon-hd-7990-crossfire-overheat,3539.html