I just wanted to sanity check this against my understanding of memory DIMM configuration for my Dell r710.

I have currently got installed 8 x 16GB DIMMs (Hynix HMT42GR7BMR4C-G7).

I purchased an additional 8 x 16GB DIMMs (Hynix HMT42GR7BMR4A-G7).

I was hoping to make use of all 16 DIMMs to achieve a total of 256GB usable memory (this is for a nested vSphere environment). However, after several attempts to find a working configuration/placement of DIMMs I have come to believe that I am unable to make use of the 3rd slot in each channel due to the first 2 DIMMs (one from each model mentioned above) being quad rank.

Each channel can only support 8 ranks.

Am I correct in thinking that due to this limitation I can only populate 2 of the 3 DIMM slots in each channel? Thus 32GB per channel, 3 channels per CPU (total of 96GB), giving a total usable value of 192GB?

Is it possible to find DIMMs with lower ranks? ie 16GB DIMMs with only dual rank or something like that so I could make 256GB from 16GB DIMMs?


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Yes, as long your configuration includes Quad-Rank DIMMs, you can populate only two slots per channel.
And it gives you maximum 96GB per CPU, so total would be 192GB, which is the maximum configurable size with quad-rank memory as per the P.129 owner's manual.

So if you need to get 256GB with 16GB DIMMs, you need to use Dual-rank, which you can find here.

  • it mentions in the manual that Single-Rank and Dual-Rank RDIMMs are supported in 2GB, 4GB, and 8GB sticks. Does this mean that I can't use Dual-Rank 16GB DIMMs to make say 256GB (128GB per CPU)? – Kane Charles Aug 29 '17 at 3:13
  • 1
    Sorry, you can check technical guide, it says "Up to 288 GB of RDIMM memory (eighteen 16 GB dual rank RDIMMs)". – shogo2022 Aug 29 '17 at 7:49

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