I have 2 identical R420 here, I bought them together. They came with 32gb each (4x8gb) and once I was going to use only one of the servers initially, I removed all the memories from the R420 B and placed them in the R420 A in order to make it 64gb. After a few days of problems I found out that I was having some errors related to memory, saw it in the BIOS. The problem only vanished after I removed the memories from R420 B out of R420 A. They were identical, same timings, same everything. The only difference from one to another were 1 digit from the memory code (the "M393B1K70DH0-YK0").
thing is: now I want to start using the R420B but I want it to have 64gb of ram, so Im willing to buy extra 32gb for it... But I have no idea on how choose memory chips that are going to work perfectly together with the chips already installed in this machine... Every vendor in the Internet tells me the chips they are trying to sell me are going to work just fine, even if the codes of theirs memories are different from the ones I have.
How can I be 100% sure a certain memory model will work fine together with the ones I already have installed in this machine?
the chips themselves:
How many CPU did you have one the server? Can you also share which all slots you populated memory when all memory are moved to one server. You can refer below links for memory configuration guidelines for R420. Can you also ensure BIOS and iDRAC FW are updated to the latest
before to answer your questions let me add more pictures. I opened the R420A (that is operating) and took some pictures of the memories, so now we have pictures of both R420A's and R420B's memories.
As you can see, the "model" is identical, both are "m393b1k70dh0-yk0". I said they werent, I was wrong about that. What each set of memory differs from eachother is that codes I underlined in red. So, now Im not sure if I need to buy another 4x8gb set with EXACTLY the same code of the set installed in the machine I want to upgrade.
About your questions:
Q: How many CPU did you have one the server?
A: 2 CPUs on each server
Q:Can you also share which all slots you populated memory when all memory are moved to one server.
A: I dont remember but I must have tried every single possible combination of slots, Ive spent a whole day trying to fix that after I found out my problem was memory related.
Q: You can refer below links for memory configuration guidelines for R420. Can you also ensure BIOS and iDRAC FW are updated to the latest
A: Ive updated everything possible in the machine at the time, that was early 2021 I think.
Gotta check these guidelines you linked, thanks
Both memory looks to be same. On other side of the DIMM is there any Dell Part number mentioned. If yes can you share the part number of the DIMM from both system. Can you try below tests also?
I cant do any tests involving the R420A anymore because its online actually. Cant be turned off.
About seeing the other side of the DIMM, I can check that on the R420B but I cant on the R420A because its in a rack where I can only have access to the server by the front side, right side and back side, I cant get myself at the left side of it to be able to take the shots you want to see. I will come by later with the numbers for the R420B's memories.
Ive bough 4x8gb from a vendor that guaranteed me it would to work, so lets wait it arrive and see. Meanwhile I gotta test the slots configuration with these 4 memories the R420B have, in order to understand better how it works. Can you suggest me which memory tests I can run while tweaking the memory between the slots, to be able to know which configurations are error free and which are not? I dont remember how Ive checked that in the past. It was some built-in tool, thats all I remember. I also remember I tested a lot with memtest86 and it never returned any error, I lost a lot of time testing it it when I had that problem in the past haha:|
If you want to test 4 X 8GB then use slot A1,A2,B1 and B2. If you want to try 8 X 8GB then use A1,A2,A3,A4,B1,B2,B3 and B4