All FX CPUs can handle DDR3-1866 just fine, but not everyone has the experience to understand how to set it up properly. It is not plug and play, so people can run into issues, or they assume it should just run at DDR3-1866 after they install the RAM. For some better motherboards, there is more BIOS control options than some basic motherboards, so that also makes things easier. But like I said, we can make sure the computer runs at maximum performance depending on the hardware used.
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