Question about crossfire performance..

[Rick54]

I have question regarding the crossfire performance..i have 2 7970ghz edition in crossfire mode in one system and have gtx 970 in other system..one with crossfire setup gives me same fps in most games as one gtx 970.i though if i add 2 cards it should be faster than 970..i play on 1080p resolution most games..system spec that my 7970 are in 4790k running at 4.4 16gb ram MSI Z97 G45 gaming mobo..http://www.tomshardware.com/reviews/radeon-r9-290-review-benchmark,3659-6.html..i couldnt find 7970 crossfire but i found 7990 performance..according to this 7990 is beating 290x and i know 290x and 970 are very close in gaming..so am i doing something wrong..do i need to change something in bios...please advise..

 

[Rick54]

any suggestion guys..if i am doing something wrong..