I have a bought a Dell R710 that came delivered with 32 GB memory. It is running VMware and I wanted to upgrade it to 48 GB RAM.
From Dell it was set up with 8 x 4GB RAM in the two channels next to the prosessor and running in Advanced ECC mode. I first installed the 4 new memory in the third channel but received an error message that this configuration can not support 128-bit Advanced ECC Mode. So I changed the location of the memory and filled up the two channels next to the prosessors so that the third channel channels on both sides are empty.
Now it works in Advanced ECC Mode but from what I can see in the documentation the memory speed drops from 1067 MHz to 800 MHz when two channels are filled completely.
So what is the best performance to install memory modules? If I install two memory modules in each channel I get 1067 MHz instead of 800 MHz but will have to change memory mode to "Optimized mode" instead of "Advanced ECC Mode". I guess there is some advantages running in "Advanced ECC Mode" but is it worth dropping the memory speed from 1067 MHz to 800 MHz?