R720XD can't get 768GB Memory.

Question

Hello,So, i have an R720XD server and im trying to get 768GB RAM Memory (24x32GB) and, when i put 16x32 memory, its everything okay, server telling me I have 512GB RAM Memory, but when i start added another rams, to the 'Green slots' amount of ram start goes to random (386GB/256GB) and i just cant get more than 512GB ram, i use 2xE5-2690v2, bios is the nevest (2.9.0) and memory what i use is all 24 pieces of 32GB 4Rx4 PC3L-10600R-9-12-AB0. HMT84GR7MMR4A - H9 D8 AG . Any ideas why? Of course idrac didnt post any troubles, but im getting message from start. That 'Warning: The number of ranks on this device is not supported.' So, how can i get 768GB Ram when 32GB memory stick have 4Rx4 or 4Rx8 ?

Dell-DylanJ · Accepted Answer

It looks like the DIMMs you're using are RDIMMs and not LRDIMMs. All the DIMMs I'm seeing for this capacity are LRDIMMs. The manual indicates that 16GB RDIMMs are not supported, so I would suspect that 32GB RDIMMs would not be, either. I would use the 768GB config from the sample document page. The only difference I see is the use of LRDIMMs, as opposed to LRDIMMs.

R720XD Manual (sample memory config page) https://dell.to/3vKbuLT

If you don't mind sharing a SupportAssist collection form the iDRAC, you're welcome to PM me. We can work out a way for you to share that and I can see if the logs offer any additional detail about the memory error.

DELL-Shine K · Answer

Can you check below link to see the memory installation guidelines

https://www.dell.com/support/manuals/en-us/poweredge-r720/720720xdom/general-memory-module-installation-guidelines?guid=guid-0f97a40c-2a63-4dc8-a8b2-607006d75804&lang=en-us

If you have quad-rank DIMM we can populate only 8 DIMM per CPU (A1-A8 for CPU1 and B1-B8 for CPU2).

Up to two quad-rank RDIMMs and up to three dual- or single-rank RDIMMs can be populated per channel. When a quad-rank RDIMM is populated in the first slot with white release levers, the third DIMM slot in the channel with green release levers cannot be populated.

MountaiNN · Answer

Hi @Dell-DylanJ ,Like i said, theres no logs in idrac, only from boot on start server, you know after information about bios version, processors HZ and amount of memory, right after that i had that comuunicate. Okay then ill buy some LRDIMMs and let you know if is that work. If that will work fine i will accept your post as solution, if not, i will ask more information

MountaiNN · Answer

@DELL-Shine K Thats kinda helpful info, but like you probably read ealier i need to use that 'LRDIMM' memory sticks, we will se if that change anthing :).

DELL-Joey C · Answer

Hi,

We will wait for you response after getting some compatible memories and check on the issue. In case if you still face any issues, what Dylan meant was about collecting iDRAC logs and upload it to the our FTP server for analysis. Here's the steps for collection: https://dell.to/3piwVkL and upload the file to https://upload.dell.com/

MountaiNN · Answer

Okay, that works, that was just because memory was RDIMM, instead of LRDIMM. When i bought LRDIMM memory everything work :). Thanks, ill use this as soultion

PowerEdge Hardware General

R720XD can't get 768GB Memory.

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