If Intel based go into BIOS and enable XMP and select profile 1, If AMD and system supports one of the following (DOCP, EOCP, XMP) then enable and select 1600 - else let us know what CPU, mobo, and DRAM model number
For a program to see, download CPU-Z (free) and in the memory tab it will show true freq - will need to take true freq times two for effective freq i.e. 667 x 2 = 1334 (1333 effective)