The specs for the 7910 here call for RDIMM and LR-DIMM ECC RAM. Are you sure that the new RAM meets those requirements as non-compatible RAM will certainly cause errors.

The ram I’ve used was listed as ecc registered dimm. The additional ram I purchased was the same. I would imagine if these were incompatible modules I wouldn’t be able to run them at all? But the machine is allowing me to use them on different channels. Up to 32GB. So I have to use a black and white slot on each section to get 32. I can’t use all white (like you’re supposed to do). Baffling. 

Any ideas what could be causing this? Is it intact the memory specifications now allowing to expand to 64? Or is it a computer problem? 

It’s driving me nuts. Thinking about scratching the 64 idea and just sticking with 32. 

according to the official ram config table, filling all slots with 4gb sticks is one of the 2 supported configurations to reach 64gb on a dual cpu system.

You sure you are not mixing LRDimms and Rdimms ? ecc aside, all modules must be either rdimms or lrdimms , not a mix of the 2

This is possibly the source of my confusion.

So even if a memory module is ECC registered, that does not mean it's RDIMM... which I was unaware of.

I read that as well that the T7910 only takes Rdimm or LRdimm....  But if I had some UDIMM. would that even run in my system? 

I went back and checked the purchases, and while they are ecc registered, they say DIMM under the form factor. Not RDIMM.. But I would imagine my system wouldn't take them at all if that was the case?

No, the manual is very clear. The system can use only Rdimm and Lrdimm , and they cannot absolutely be mixed. So only one, or only the other

All the modules I have are ECC Registered, but none say RDIMM or LRDIMM on the form factor section...  Reading up on it, ECC Registered does not mean it is RDIMM. But from what I see from sellers, I"m not sure everyone is aware of this difference? (I'm not even sure I'm correct). 

That being said, if nothing I have is RDIMM, how is it working in my machine to give me the 32GB? Is it RDIMM then and just mislabeled? 

Thank you for the feedback. 

The ram preinstalled has a part number on it, write it here ( brand + pn ) , same goes for the ram you purchased

Had a friend help build the computer, internal drives, gfx card, memory, etc... so he started off with:

2 of:
4GB Hynix 1Rx8 PC4 - 2133P - RD0 - 11
HMA451R7AFR8N - TF TD AB 1620

2 of:
4GB Hynix 1Rx8 PC4 - 2133P - RD0 - 10
HMA451R7MFR8N - TF TD AB 1537

To keep it uniform I bought new modules with:
4GB Hynix 1Rx8 PC4 - 2133P - RD0 - 11
HMA451R7AFR8N - TF TD AB 1620 and some with 1616 on the end here.

All of the above will work if I keep them on particular channels = 32GB. But as soon as I add more, even if the same P/N numbers, it rejects them. 

HMA451R7AFR8N ecc registered Rdimms , mmmm

same for the other p/n

I'm definitely at a loss...

Would resetting the CMOS do anything? 

in theory no, shouldn't change things

With the T7910 released back in 2014, it won't hurt to change the battery with a new one if it's 5+ years old.  Note any special settings you set in BIOS first, as it will reset.  No guarantees new battery will change anything, but can sometimes be the 1st thing to troubleshoot as bad batteries can cause bizarre problems.

Hi @mazzinia or @JOcean,

I'm not quite 100% on this one - I believe RAID setup will still be there if CMOS battery is changed, won't it?  I haven't heard yet of it going away just by changing battery.

Thanks for the tip. I'll probably give it a try...

I do have internal RAID 0 I've set up through the bios... Will changing the battery screw those up at all? Or will they be okay? Or is it 50/50 haha. 

Thanks again.

From what I have read in other posts in the forum @bradthetechnut , the default setting in the BIOS from Dell is RAID so it should not be affected with the battery change.