R620 memory issue

Have r620 that i use in my home lab.  server has 192gig ram (24x 8gb pc3l-10600r).  Tried to replace these with 384gig (24x 16gb pc3l-8500r memory).  I get message in idrac console on bootup that shows each channel says exceeded maximum total number of ranks supported.  If I look at the docs https://www.dell.com/support/manuals/en-us/poweredge-r620/r620systemownersmanual-v1/system-memory?guid=guid-c93ad857-06a2-4ef8-88d7-4420451c297a&lang=en-us it would appear LRDIMM x1066 quad rank is a supported configuration.  i had upgraded the bios from 2.7 to 2.9 to make sure no and no difference.  What am i missing?