Some motherboards of GIGABYTE GA-P35-series have two PCI-E graphics slots. Intel P35 chipset officially supports ATI CrossFire, but it enables only x16+x4 lines configuration. It's not so bad as some radical benchers can think, here are some tests for example:
http://www.firingsquad.com/hardware/...e_performance/
http://www.anandtech.com/video/showdoc.aspx?i=2837
IMO, the deifference between x8+x8 or x16+x16 and x16+x4 isn't so huge to worry about. CrossFire support problems from games are more serious.