[NAME]  The service manual is wrong . . . and the DIMM slots are mislabeled.  Happy to see you figured it out and got things working properly.
I want to upgrade my 8 GB RAM to 32 GB so I bought a 32GB RAM kit (2x16GB), Corsair Vengeance LPX 3200mhz. I installed them in slot 1 and slot 2 (service manual instructions) and the PC did not boot up.  I tried just one stick in slot 1 and it worked fine, recognized 16gb at 3200 mhz.  I swapped out the other stick in slot 1 and it also worked fine.  Thinking slot 2 must be bad, I contacted Dell support.  No support since the RAM wasn't Dell, they suggested I buy Dell Ram.  Just for kicks I tried Slot 1 and Slot 3, no luck.  Then Slot 1 and slot 4, it worked great.  Recognized 32GB ant 3200mhz.  Can anyone tell me why the service manual said to use slot 1 and slot 2, but the RAM worked with Slot 1 and Slot 4?  Are these BIOS settings or pin settings on the motherboard? Thanks,
Aurora R9, Corsair ram upgrade issue