Z420 v2 RAM speed decrease with >4 DIMMs?

[n_boers]

Does RAM speed decrease when two DIMMS are on a channel? I'm looking at using 4-6 16GB PC3-14900R in a Z420 with a 2013 boot block and an E5-2687W v2. I've seen some evidence from some sources that 5 or 6  may have slower RAM speed than just the 4. One of the clearest answers I found was this from BambiBoomZ, but it includes a mix of different DIMM types, so unsure if it's the size, the rank, or the two DIMMs per channel causing the issue:

2. The 24GB of RAM to 32GB with 8X 4GB RAM modules is preferable to the 24GB. Having 24GB- 4X4GB + 4X2GB provides worse performance than 4X4GB alone. It has to do with the way the ranks are addressed when they're not equal.  Use all identical RAM modules- the same make and model and having the HP part number on it.  I had a z420 very similar to yours: z420_1 was: E5-1620 + 16GB  and later 24GB + Firepro V5900 and all the memory benchmarks were worse at 24GB than at 16GB.

6 pieces will obviously give me more RAM than 4, but will the speed suffer if they're all identical?

[DGroves]

ram speeds are controlled by the cpu in newer systems as newer cpus integrate the memory controller check the intel cpu specs for your model to see what mem speeds it supports

in general, systems with 4 dimm sockets are "dual channel"  amd inserting one dimm in channel "A" and one in channel "B"

activates the dual channel memory access, filling the other two sockets will  increase the mem capacity but not anything else

motherboard makers usually color the mem sockets differently to differentiate the two channels

please read the z420 documentation on the HP site for more information on your system