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April 3rd, 2020 06:00
Minimum RAM slot population for R720
We have a two socket Dell R720 server, with 16 "2GB PC3-12800 DDR3-1600MHz ECC Unbuffered CL11 240-Pin DIMM 1.35V Low Voltage Single Rank" RAMS.
We are planning to increase the amount of RAM, and found one of the online Dell documents stating that the UDIMMS can have a maximum of 64 GB, and we can't mix UDIMMS with RDIMMS/LDIMMS.
If that is correct we are left with only one option which is to yank out all the 2GB UDIMSS, and put in a couple of 16GB RDIMMS, so that we can add more when needed.
My question is:
1) can we have only four 16GB RDIMMS populated in say " A1, B1, A2, B2 white slots, while all other slots are empty? what is the minimum number of RAM slot's that need to be populated to have it working?
2) Can we have a mixed RAM setup as such: two 16GB sticks in A1,B1 and 2 GB sticks in A2,B2,A3,B3,A4,B4(all in white slots)?
DELL-Chris H
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April 3rd, 2020 13:00
Zynox202,
That document wasn't correct. The R720 supports the following
◦Up to 768GB of LRDIMM memory (24 x 32GB LRDIMMs)
◦Up to 384GB of RDIMM memory (with 24 x 16GB RDIMMs)
◦Up to 128GB of UDIMM memory (with 16 x 8GB UDIMMs)
So you have options.
To answer your questions;
1) Yes you can.
With dual procs the minimum number of dimms you can have is 2, one in A1 and one in B1
2)Yes, memory populations can be different as long as the population rules for each socket and RAS mode are followed.
Such as
•If dimms of different speeds are mixed, all channels across all CPUs operate at the slowest dimms common frequency.
•Only one type of dimm is allowed per system: UDIMM, RDIMM, or LRDIMMs. They cannot be mixed.
•DIMM slot latches/ejection tabs are color coded per PowerEdge Behavioral Specification to aid identification of proper DIMM placement. First DIMM is white, second DIMM is black, third DIMM is green.
•Advanced ECC (Lockstep, SDDCx8) and Mirror modes: Channels 0 and 1 and channels 2 and 3 must be identical channel level configurations. (See graph below)
•DIMMs must be installed in each channel starting with the DIMM farthest from the processor. DIMMs should be installed with largest rank count to smallest. For example if DR are mixed with SR DIMMs, DRs should be placed in the lowest DIMM slots, then the SR DIMMs.
Hope this helps.