Except for the speed, there should be no other restrictions (if not mixing with single/dual ranks): For quad-rank memory modules:• One memory module per channel supports up to 1067MHz.• Two memory modules per channel are limited to 800 MHz, regardless of memory module speed. Page 124 of the Hardware Owner's Manual:[URL] Also, with BIOS version 1.1.5 (almost 4 years ago), support was added for 16GB DIMM's, raising the maximum memory for the R410 to 128GB.  This specifies dual-rank, so it is unclear whether quad-rank 16GB DIMM's would also be supported, but the speed decreases likely still hold true. [URL] 
Hello there, I was searching the forums and couldn't find anything regarding quad rank ram cards and maximum ram. I have 4 PE-R410s (2 CPUs each) with 32GB of ram which is 4 x 8GB 1333MHZ Quad-Rank registered DIMMs. Now time has come that we need to max it out with the same 8GB sticks to a total of 64GB. My question is, is it possible to populate all the slots with quad-rank sticks?  Regards Sam
R410-Maximum Ram Upgrade with Quadrank DIMM