Enzorik,   You can order and use 16GB dimms in the R510. You can see the population guidelines per proc on page 117 of the guide, located here. Before upgrading the memory though, you need to be  certain that you have the server up to date on BIOS, Drac, Lifecycle Controller,  and the Raid Controller. This is to ensure that the server remains stable. Let me know if this answers your question.
Hello. There are two Dell Poweredge R510 servers with following configuration: CPU: Intel Xeon X5675 (3.06GHz, 6C, 12Mb cache) Additional CPU: Intel Xeon X5675 (3.06GHz, 6C, 12Mb cache) 64Gb RAM per 2CPU (8x RDIMM 8Gb Dual Rank LV) 1333MHz We'd like to upgrade the servers with 128Gb RAM.  What is most suitable way to do it? Can I just order 8 modules per 16Gb RAM and replace?  Thanks in advance for your help.  
Dell Poweredge R510 memory upgrade