Yes, you can add another 8GB DIMM, but the ONLY configuration in which it will work is to put it in the fourth slot with the other memory modules.  The 4 memory slots associated with the other [missing] processor cannot be used without a processor for that bank.
Hi, I want to upgrade the memory of a PowerEdge R-410 that was bought with a single Xeon E5645 and 3 x 8 GB dual-rank RDIMM 1333MHz. The system has five free memory slots.  I want to know if I can add a single 8 GB dual-rank RDIMM 1333MHz, to bring total memory to 32GB, and if so, what is the proper configuration. Thanks in advance, Terry
Memory configuration on PowerEdge R410