It looks like some slides showing the AMD Radeon R9 290X performance results in both Uber and CrossFireX modes have been leaked. AMD recently allowed many sites to post 4K performance previews (which we covered), but some sites actually posted the entire performance presentation.
From these posted presentations we came to learn that the Radeon R9 290X actually operates under two different modes: Quite Mode and Uber Mode. Looking at the chart below we can see that Uber Mode gives a slight performance boost over Quiet Mode, but not that much. We are guessing that it is some type of power and performance management algorithm which we will only find out when the detailed reviews go live.
The second leaked slide which is below shows the R9 290X’s CrossFireX scaling performance of the card. We can see that the new CrossFireX DMA engine does a very good job in dual-GPU functionality. That is currently all we know right now about CorssFireX performance on the R9 290X.
Expect to see more information come out when reviews of the card go live later this month.