Ibeng, The 5620 does support them. Be sure to update the server as well.  I would suggest Optimized for capacity, as well as spreading them across the multiple channels.
Hello, I am looking for guidelines of how to setup and install 16GB ram sticks on my R710. The goal is reach 96GB total RAM. Following some posts, i realized R710 with ECC is unsupported using16GB sticks, so I'm looking for the correct setup for optimizer mode with 6x16GB and a setup for 2x16GB+4x8GB.  Any suggestions? Thanks!~  
R710 RAM SETUP