Here is the memory module guidelines for your system.  Channel 0 is located next to PCIe slots, starting with Dimm 1.  The Dimm info should be imprinted on motherboard and side panel.   [IMAGE]
I've just picked up a t 7910 that was running with 32GB. Single CPU, nothing fancy but something to replace my old, slower system with. I do a lot of spreadsheet work and that old 8GB system wasn't cutting it. The Dell came with 32GB memory installed and I purchased another 32 to add to it. My issuer is that I know there is a pattern to add memory but I can find no diagrams to indicate which channels are which.. I found a diagram for a R7910 but that was no help. Just need to know which is Channel 0 and the slots assigned to each channel. Thanks, TheOldPuterMan  
T7910 memory configuration