do you have to have 2 of the same card to use crossfire?

do you have to use 2 of the same card to use crossfire? (eg 2x x1900xtx's in crossfire).

or is it possible to combine cards (eg, x1900xtx + x850 or whatever crossfire supported card)

if so, any speculations on performance?

so basically i cant even do crossfire with 2 x1900xtx 's, i have to have a x1900 crossfire edition and a x1900xtx?

I seem to recall that you CAN use an x1300 or x1600 with an x1800 crossfire edition, but that information may have been speculation prior to release. In reality, you would NEVER want to do that even if it accepted.

The new GTO's can be used without a crossfire edition, but it might require the x32 pcie mobo's instead of the original x16's. I have heard rumors that regular x1800xt's and x1800xl's will be allowed to do this also (in upcoming driver update). The problem is that the PCIE interface will become a bottleneck that the crossfire edition was designed to releive.

When ATI/AMD release driver updates for physics processing, you will be able to pair an x1300 or x1600 (or whatever you have to spare) with an x1800 or x1900 or whatever comes next and use the lesser card for physics processing (but not an 850, x1x00 and above they say).