CrossFire in Practice: Radeon HD 4850 CF vs 6850
 

We've gone through all the advantages and disadvantages of SLI and
Crossfire modes many times by now. We've even had an article on the
Hydra chip present on MSI motherboards, which enables AMD and NVIDIA
graphics to work in conjunction with more or less tangible results…

The technology has matured long ago, drivers are refreshed on a regular
basis, and this continual process seems to be reliable enough for you to
be able to trust AMD to keep delivering in the future.

http://www.insidehw.com/Reviews/Grap...F-vs-6850.html