looks like the 512 gts in sli is faster at 2.0 than everything else thats some differences in speed!!
http://www.tomshardware.co.uk/PCI-Express-2-0-Crossfire,review-29948-7.html
Quoted from thg
Our switch to the X38 chipset for Crossfire tests was overdue. The dual x16 connections improve performance by 6 to 7.7 percent on average, while optimized games such as Call of Duty 4 run nearly 20 percent faster. Looking only at games and resolutions that show a tangible performance boost, we saw an improvement of 12 to 15 percent on average.
Another thing we saw is that a dual x16 configuration is not as effective for Crossfire as a single x16 slot is for a single card. As mentioned above, a single card loses between 7 and 8 percent performance when operating in an x8 slot. Moving from an x8 + x8 setup to an x16 + x16 connection also only yielded a 7.7 percent frame rate increase, though, and not twice as much, which we would have expected based on the single card results
http://www.tomshardware.co.uk/PCI-Express-2-0-Crossfire,review-29948-7.html
Quoted from thg
Our switch to the X38 chipset for Crossfire tests was overdue. The dual x16 connections improve performance by 6 to 7.7 percent on average, while optimized games such as Call of Duty 4 run nearly 20 percent faster. Looking only at games and resolutions that show a tangible performance boost, we saw an improvement of 12 to 15 percent on average.
Another thing we saw is that a dual x16 configuration is not as effective for Crossfire as a single x16 slot is for a single card. As mentioned above, a single card loses between 7 and 8 percent performance when operating in an x8 slot. Moving from an x8 + x8 setup to an x16 + x16 connection also only yielded a 7.7 percent frame rate increase, though, and not twice as much, which we would have expected based on the single card results
