Sorry, mate, "it was built for 1333MHz" - I did messed up there...

my bad...
As you can see on the manufacturer's site (
http://www.amd.com/us/products/deskt...omparison.aspx), the FX series CPUs should support "up to DDR3 1866" - with the note: "1866 supported with 1 DPC (DIMM per Channel) in single memory slot motherboard designs"
Sincerely, I don't think if you would notice the difference between 1333MHZ and 1866MHZ in every day use... What you could observe, are the timings of the memory... But even that would be more observable at benchmarks...
In addition to the previous link, this one also may help in understanding the settings and OC'ing:
http://rog.asus.com/forum/showthread...e-Overclocking