Fganter.  Unfortunately populating three memory modules per channel is not supported at 1.35 V. Systems with 1.35 V memory will also operate the memory modules at 1.5 V if any of the following conditions exist: Hope this helps clarify the situation.
I'm noticing that when populating the first DIMM in each channel (i.e. 3 of the 4 memory slots per processor) with PC3L memory, it runs at 1.35V, as it should. When I add a DIMM to the fourth slot, memory runs at 1.5V, thereby disregarding the low voltage benefit. The T410 technical guide says "When operating at the lower voltage, additional frequency and population restrictions can take effect."  Is filling all memory slots considered a population restriction in this context?   Seems like a pretty common thing to do (filling all memory slots)... Thanks
Supported Low Voltage Memory (PC3L) Configurations for PowerEdge T410