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8 Posts


May 9th, 2023 12:00

Is there anything I should be aware of when increasing RAM on our R350 server?

Hi Emmet and the rest of you all in server-land.. 

The other thing we're looking to do is to increase the 8Gb of RAM that is in our server to something more.. the only options that the dell store lists for this server are :

  • 8Gb modules
  • 16Gb modules
  • 32Gb modules

In looking at the hardware inventory on iDRAC9 I see two single-rank DIMMS (A1, A2) populated with 8Gb DIMMs.

If we want to move to 16Gb I'm assuming that we'd need to buy two 8Gb modules to add to the existing 8Gb pair making a total of 16Gb (???).

Yes, I'll admit that I'm a bit confused on the single-rank vs dual-rank DIMMs and if there's any difference between the actual DIMM or just where they're plugged in on the system board or ??...

I see the spec's for the R350 server indicates the max memory with a dual-rank setup is 128Gb whereas the max memory with a single-rank setup is 64Gb. I guess I'm wondering what our options are here in light of the fact that we've already got the two single-rank DIMMs installed.  Maybe we need to get rid of those or ...

I flipped open to the service manual for this server and a bit more description is available there.  There, the manual talks about channel A & B for the two memory channels with four slots (A1, A2, A3, A4). I'm not sure how that is different from single vs dual ranking or perhaps they're not associated with each other... 

Once I get past that hurdle, is there anything I need to know to do the swap aside from taking the usual anti-static precautions after the server is disconnected from power and so forth?

Thank you!!

16 Posts

11-05-2023 09:00 AM

Hey Rick


This all comes down to population rules and what is and isn’t possible with DDR4 memory.


The R350 has two memory channels , Channel A consists of A1 & A3 Channel B consists of A2 & A4. With DDR4 the memory is interleaved by “banks”.  The R350 has two banks, one bank is comprised of the two white slots ( A1 and A2 ) the second Bank is the black slots(A3 & A4 ).


With DDR 4 you can mix channels but not banks. In other words, the two white slots must be identical to each other as they are interleaved and likewise the two black slots must also be identical to each other. But the channels can be mixed i.e., you can have 16GB (single rank) or a 32GB (dual rank) DIMM in A1 (white slot) and an 8GB (single rank) DIMM in A3 (Black slot) but then channel B must be identical to Channel A i.e.  A2 needs to be the same as A1 and A4 needs to be the same as A3.




Example of supported configuration





Example below of an Unsupported configuration


White slots are not identical to each other, and the black slots are also not identical to each other.





To summarise


  • Channels can be mixed i.e., they can contain different capacity DIMMS and different rank DIMM’s, but banks need to be identical
  • Always populate the white slots with the high-capacity DIMM’s – i.e., in the example above of a supported configuration the 32GB DIMM’s are populated in the white slots A1 and A2, and the lower capacity 8GB DIMMs are populated in the Black slots
  • Always make sure the DIMMs are the same technology i.e., we only support DDR4 UDIMMS with the R350 but you can buy RDIMMS and LRDIMMS on other sites. You must make sure that the new DIMMS regardless of rank or capacity are also UDIMMS.


Just finally in response to your comment regarding “I see the spec's for the R350 server indicates the max memory with a dual-rank setup is 128Gb whereas the max memory with a single-rank setup is 64Gb”

The memory we sell for the R350 is as follows

DDR4 – 8GB UDIMM – single rank

DDR4 – 16GB UDIMM – single rank

DDR4 – 32GB UDIMM – Dual rank


So, if you went with all Dual rank DIMM's you would have to remove the two 8GB DIMM’s currently in the system and install 4 x 32GB DIMM’s which would give you the max supported capacity of 128GB or you could insert 2x32GB DIMMs and keep the remaining 2 x 8GB DIMM’s to give a total capacity of 80GB

Without getting to technical the difference between single rank and dual rank is the amount of DRAM chips on the DIMM, a single rank has 9 DRAM chips, 8 for data and one chip for ECC, with dual rank there’s 18 chips - 9 for each rank.  In general, the more ranks on a DIMM the more capacity they have.





Kind regards



8 Posts

11-05-2023 11:00 AM

Thank you very very very much Emmet!  You're so helpful!!  

16 Posts

12-05-2023 08:00 AM

Hey Rick - no problem at all   

12-05-2023 17:00 PM

Great explanation Emmet,

I often wondered about those memory population rules, many thanks for sharing

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