Mr Hosting, With the processor configuration, along with the existing configuration, you wouldn't be able to add 4 4GB dimms. You would either have to add 6 4gb dimms or 2 4GB dimms. This is going to be due to the memory rule that you have to equally populate the 3 memory channels. With that beening said, the dimms would be populated as one of the following ; Adding 6 4GB dimms (Both result in 48GB) A1, A4, A7, A2, A5, and A8  / B1, B4, B7, B2, B5 and B8 or  A1, A4, A2, A5, A3, and A6  / B1, B4, B2, B5, B3 and B6  Adding 2 4GB dimms A1, A4, A2 and A5  /  B1, B4, B2, and B5  Let me know if this helps clarify.
Hi, Our PowerEdge R710 has 2 E5620 processors and 24GB RAM (6x 4GB Dual Rank DDR3 Synchronous Registered 1333MHz). Memory is set to Optimizer mode and is using the following memory sockets: Within the next 12 hours we want to add 4x 4GB additional RAM (identical modules) so that we have 40GB RAM instead of 24GB. The Hardware Owner's Manual is only giving configurations for 32GB or 48GB RAM. Which sockets should be used? Is the following configuration correct? 
PowerEdge R710 upgrade RAM 24GB to 40GB