2166 maybe that maximum supported by the CPU, just like on my motherboard CPU combo (Asus Sabertooth Z97/4790K), but with the motherboard you can run the RAM a lot faster than potentially recommended without too much trouble. On mine, the motherboard lists 1866 as the maximum, and I believe it's 1866 for the processor too (might be off on that one, might be 1600), but I'm running 2133 just fine. It will put a little more stress on the CPUs memory manager or whatever the fancy name is, but other than that, no worries, and if you have adequate cooling, which you should for an unlocked CPU, there should be no worries at all. I'd worry more about compatibility of the RAM at that speed. Haven't read much on the dual channel DDR4 memory only the quad channel. Worst case scenario, you may have to run the RAM a little slower than it's rated speed for stability. The good news is that RAM speed doesn't effect your experience much. The difference between the bestest and worstest RAM is only a few percent.