|Are you asking about the MSI 970A-G43 board you mentioned in your other post? Notice the memory spec >> "Supports four unbuffered DIMM of 1.5 Volt DDR3 1066/1333/1600/1866/2133* (OC) DRAM"|
A few things are in play here:
1st of all, notice that to be able to run the DDR3-2133 RAM, it has to be overclocked. "Overclocked" probably isn't the best term because you don't have to overclock DDR3-2133 to get it to run at 2133MHz (1066MHz freq). What it really means is the BIOS RAM settings will have to be manually configured to get it to run at the proper speed.
2nd, notice the board specs the RAM voltage at 1.5v. That means the only official JEDEC RAM is supported & the max limit for JEDEC DDR3 is 2133. If you check the voltage for any of the higher speed RAM (DDR3-2400, 2666, 3000, etc), you'll see it's 1.65v or higher.
3rd, the memory controller is in the CPU not the motherboard. The FX-series (with the exception of the FX-9590) only officially supports up to DDR3-1866.
Why do you feel you need faster RAM?