Abidal,   Even with the CPU supporting the dimms, it is limited at the server. With 3 LR dimms populated in the same channel, the server limits 1.5v dimms to 1333. You can see this on page 46 of the manual here.    Let me know if this helps.    
Hi, I have a R820 equipped with 4 x E5-4627 v2. I installed 48x32Gb RAM to attempt the max of 1.5Tb.  The RAM I'm using is JGGRT:  Pc3-14900 DDR3-1866 mhz. When I boot the machine I'm getting RAM running at 1333 instead 1866. The CPU, as I found in intel website, supports 1866 Mhz. Can someone tell me what I'm missing? Thank you.
R820 RAM 1866 Mhz running at 1333 Mhz