Loads on memory bus still a concern?
On my AMD Bulldozer era system using DDR3, DRAM speed is very sensitive to the number of loads on the memory bus. By limiting memory to only 2 of the 4 available slots, my system can maintain 1600 MHz speed. If I occupy all 4 slots with the exact same memory, speed drops to 1066 MHz on all slots.
I'm assuming the constraints with loads still holds true with NVDIMMs? I did a quick search on the topic, and couldn't find any information. Seems to lessen the appeal if adding NVDIMMs slows down the entire memory bus.