Proliant gen8 don't recognize 2 x 8gb ram

Good morning,
I've a MicroServer proliant Gen8 with Intel(R) Xeon(R) CPU E3-1220L V2 @ 2.30GHz processor.
Total memory is 16 gb

Processor 1  1   Good, In Use  Yes  647658-081   DIMM DDR3  8192 MB  1333 MHz  1.5 V  2  UDIMM  Processor 1  2   Good, In Use  Yes  647650-071   DIMM DDR3  8192 MB  1333 MHz  1.5 V  2  RDIMM 

But at boot I see only 8gb installed

There is a memory mirroring? If yes ..How can I solve the problem.

Best regards

Davide

p.s. sorry for my bad english