When I boot up X5DP8-G2, the system has no display and only gives beeps indicating no memory installed, but the system indeed has a pair of recommended memory populated.
Please make sure that at least 2 memory modules are populated in DIMM1A and DIMM1B which are located far away from the chipset. X5DP8-G2 only supports in-order memory installation which means that you have to install modules from DIMM1A, DIMM1B, then DIMM2A, DIMM2B and so forth.