Hello Jancic,   I would recommend at your soonest maintenance window to change the memory population to follow the rules to match what you post: 16 GB modules should be installed in A1-A4 and B1 to B4 8 GB modules should be installed in A5-A12 and B5 to B12   NOTE: Memory configurations that fail to observe these guidelines can prevent your system from booting, hanging during memory configuration, or operating with reduced memory.
Hi, We upgraded memory to our PowerEdge R730 ,  ESXi 6.0.0 production server. Before upgrade it has 16 x 8GB of RAM, DDR-4, single Rank, RDIMM modules, installed in A1 to A8 and B1 to B8 sockets. We added 8 x 16GB RAM , DDR-4, single Rank, RDIMM modules, and installed in A9 to A12 and B9 to B12 sockets. We have the following warning during boot and recorded in Lifecycle log for every memory slot which is populated with new 16GB modules (A9-A12 and B9-B2) : "UEFI0104 The DIMM module on memory slot (A9-12 or B9-12) is populated out of order in the DIM channel." After the boot , Server itself and ESXi server correctly recognize total amount of memory and there are no other warnings or errors. We asume that this warning is because as per documentation memory modules with larger capacity should be installed in first slots (in our case 16 GB modules should be installed in A1-A4 and B1 to B4)and then memory modules with lower capacity should be installed (in our case in A5-A12 and B5 to B12). My question is, is it safe to leave the memory as it is, since it is a production server and we don't want to shut it down again, and there are no problems in last 24h since the upgrade was done? Can this warning be ignored in this case?   Thank you,  Kind regards, Jancic    
Upgrading memory of PowerEdge R730