(Redirected) DIMM Slot on Poweredge R720

Currently I just procure 8*8 GB additional RAMs and piled on to my Poweredge R720 with single processor which already occupied 8 DIMMs with 8*8 GB DDR3 Rams. After installed I just able to acquire only 12*8 (DIMM_A1-A12) RAM on my server whereas rest 4*8 RAM unable to piled.  Is their any-workaround available that I can able to compile rest of the  DiMM_B1- B12  DIMM slot to my existing Processor. Seeking any expert advise to cater this obscurity. 

Thanks in advance.