Yes why my memory run max 1400Mhz not 1600Mhz
Maybe overclock?
Yes ,FSB increase changes the RAM ratio.
Put FSB at 200 the default value and set the RAM in the section reserved for it.
The UEFI BIOS is some how strange but using manual setting for RAM should unlock the RAM adjustment.
It s an easy one you just set 1333 or 1600 or 1866 ,nothing ore to do.
The manual should let you know exactly what and how to do.