AMD doesn't support xmp profile ram but can manually set in bios via cpy bus speed or ram divider as lengchai mentioned.

Try increase ur bus speed (will auto increase HTT, cpu clock speed and ram speed as well). When u see ur ram speed reach 1866, decrease ur HTT and cpu clock speed near to default or speed that u needed using multiplier as ur cpu ar unlockable multiplier (black edition). Also u need to increase a bit north bridge freq as ur bus speed increased.