It's a nf200 board so yes, it'll do x16/x16. With that being said unless you're running at Eyefinity resolutions there's tons of evidence showing that x8 lanes aren't bottlenecks. There's also evidence that the nf200 chip adds its own overhead actually losing performance vs x8/x8. Again, this might change at Eyefinity resolutions but it hasn't been tested recently or on modern cards. The last time it was thoroughly benched was done using 2x GTX480 in SLI.
Bottom line, if you're using anything under 2560x1600, forget about x16/x16 as it doesn't matter.