I dont mean to sound doubting however, I know of other boards based on the C602 chipset that im sure are nearly identicle trace wise and hardware wise to the 2600cr2. This board is marketed as a Workstation board (The S2600IP being the server variant) with 4 double spaced PCIE X16 slots i cannot possibly see how Crossfire wouldnt be supported. Does it support Nvidia SLI? ...I love team intel, but i gotta say this is very unexpected. It is one thing not to be certified for crossfire and or SLI, but what about this board would prevent the cards from linking up, is it a bios option or was this deliberately circumvented in the firmware.
Thanks for your tolerance, haha.
To answer your question, according to the Technical Product Specification for the server board; it does not offer any kind of option in the BIOS to link two different cards together as you are looking for: