DRAM DIMM installation rules
For RDIMMs or LRDIMMs, the following memory modes are available:
All DIMMs to be installed must be the same type. Do not mix RDIMM and LRDIMM in the same server.
When you install DIMMs with same rank and different capacity, install the DIMM that has the highest capacity first.
When you install DIMMs with different rank, install the DIMM with highest rank first.