T7820 128GB Intel Optane Persistent DCPMM memory module Install, Help Needed to Post!

Hi Folks,

Can someone please tell me how to install these 128GB Optane persistent memory modules

https://www.dell.com/en-uk/shop/dell-memory-upgrade-128gb-2666mhz-intel-opt-dc-persistent-memory-cascade-lake-only/apd/aa664973/memory

They are listed as supported for the Dell T7820, however I get no post when I try installing them in either singles or in a pair. I have manged to get 64GB RDimms and 128GB LRDimms (non optane ones) to boot in this system, but not these optane memory modules.

Currently I am running single CPU whiich is an Intel Xeon 4215 which has support for the optane memory modules

https://ark.intel.com/content/www/us/en/ark/products/193389/intel-xeon-silver-4215-processor-11m-cache-2-50-ghz.html

I'm thinking its one of two things,

1. Ram speed and CPU rated speeds, ram speed is 2666Mhz, Max CPU speed is 2400Mhz, however from past experience I have never known ram no to drop down one /two levels from its rated speed.

2. I looked up the manual in the Dell Precision 7920 and gives a detailed breakdown (on page 14) that RDimms are used as cache to run the Optane memory modules, which means you need to mix RDimms with Optane memory modules, weird as I've never heard of mixing memory types before.

https://www.delltechnologies.com/asset/en-us/products/workstations/technical-support/Precision_7920_Tower_Technical_Guidebook.pdf

I can seem to find this manual section for the Dell Precision 7820

I'm wondering if anyone here has actual first hand knowledge of an install like this or has some knowledge that can help. Thanks for your time and help

Kind Regards, Abdul