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August 13th, 2025 13:50
PE R650 Unsupported Memory Configuration after adding DIMMs
We have a Poweredge R650 with a single CPU and 128GB of RAM, and are looking to add 32GB to it.
The 16 stock DIMMs are installed into slots:
A4, A8, A2, A6
A3, A7, A1, A5
According to the docs, this represents one DIMM installed for each channel. We are trying to add two 16GB DIMMS (Dell M04W6) to the system. As I understand it, the new modules should be installed into A9 and A10.
But when booting the server after adding these modules, it throws an unsupported memory configuration error. So I'm a bit at a loss as to how to resolve this, and would appreciate any advice.
Thanks
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DELL-Charles R
Moderator
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4.5K Posts
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August 13th, 2025 17:55
Hello,
You have unbalanced channels (some channels with 2 DIMMs, others with 1)
This violates Dell’s memory population rules, which require:
Equal number of DIMMs per channel
Matching DIMM capacities per channel
Valid total DIMM count, quantity, per CPU ( 1, 2, 4, 6, 8, 12, or 16)
You have Eight 16G DIMMs
Your next step would be Twelve DIMMs as shown in the righthand side of the table.
So you would need to add 4 DIMMs: A9,A10,A11,A12,
General memory module installation guidelines:
https://www.dell.com/support/manuals/en-us/poweredge-r650/per650_ism_pub/general-memory-module-installation-guidelines?guid=guid-6db30d04-e447-48c6-8748-d6389f356fdb
DELL-Rey G
3 Apprentice
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1K Posts
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August 13th, 2025 21:48
try this page, it might be a clearer about how the channels are populated:
https://www.dell.com/support/manuals/en-us/poweredge-r650/per650_ism_pub/system-memory-guidelines?guid=guid-4958f7cf-21b1-4c00-97e8-4ce708068c77&lang=en-us
Rey
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