Both first hand experience and an understanding of the architecture. The memory controller on the 55xx processors can't address 16gb per DIMM. While this poster might have gotten the 16gb DIMMs to work he probably forgot to look at see that he was only getting 8gb/DIMM available at the CPU.The reason I re-asked the question is because of the following posts on page 32. PigLover - are you saying this because you tried or are the posts below not accurate?
Note that this same poster claimed elsewhere that he used DIMMs from both CPU banks with only one CPU installed...which is clearly FUD since the intel EP/QPI architecture makes this quite impossible.