Crossfire x8+x8 versus x16+x16

Overall, the change in platforms results in a speedup of only a few percent.

Games that ran smoothly before run a little faster, while slower games such as Crysis or Flight Simulator X don’t yet benefit from Crossfire optimizations in the WHQL drivers.

Currently, going from x8 to x16 for Crossfire really only offers a tangible payoff in higher resolutions.

Read more here.