Dell r740xd RAM Issues

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Propaganda

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Dec 6, 2017
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I have an r740xd (well vxrail p570f, same difference) I have some random micron 16gb rdimms (2666 and 3200 variants) I am running currently. I am trying to upgrade to 32gb rdimms. I buy a mixed lot of hynix/samsung 32gb pc4-3200aa rdimms on ebay. None of the new 32gb rdimms are recognized by my r740xd. I have never had an incompatibility where a server would not even recognize a rdimm in several different systems/manufacturers with many different rdimms over the years. Now I have 11 rdimms that won't recognize in my server. I don't have another system that will take ddr4 rdimms so I am not sure is this something wrong with Dell or could this guy have really sent me this many bad rdimms? I tried just running them 1 at a time in slot 1 and not one is utilized but if I put my old ram back it boots right up.
 

RolloZ170

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Apr 24, 2016
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what CPUs ?
NOTE: The 16Gb DRAM type module can only be supported by 2nd Generation Intel® Xeon® Scalable processors or newer.
 

Propaganda

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Dec 6, 2017
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Any chance the 32GB RDIMMS have incompatible ranks/banks? Dell site specifies 2Rx4 for 32GB modules on that model.
That might be the problem, strange though, even the r730 supports 32GB 2rx4 and 2rx8 rdimms per the technical datasheet. I do see where you got your information from but it is a strange limitation. It is also unfortunate that 1st gen scalable doesn't support 64gb rdimms; only lrdimms.
 

RolloZ170

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Using a 6132, so first gen scalable. Not using regular dram, rdimms throughout here.
32GB 2Rx4 will be OK, 72/4=18 8Gbit DRAM chips per Rank.
but 32GB 2Rx8 uses 72/8=9 16Gbit chips per Rank, need one more address line which 1st gen scalable lacks.
 

Markess

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May 19, 2018
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Northern California
That might be the problem, strange though, even the r730 supports 32GB 2rx4 and 2rx8 rdimms per the technical datasheet. I do see where you got your information from but it is a strange limitation. It is also unfortunate that 1st gen scalable doesn't support 64gb rdimms; only lrdimms.
Skylake Xeons in general had some odd memory limitations that the prior generation Haswell/Broadwell processors didn't. So, sometimes, people bought RAM that worked fine with older stuff, reasonably assuming it would work with the newer stuff... and it didn't. Ask me how I know :rolleyes:
 

Propaganda

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Dec 6, 2017
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E5 v3 runs in the same issue.
Seems like a tick (or is it a tock); where the first release on a platform is more limited for ram than the seconds. ie v1/v3/
32GB 2Rx4 will be OK, 72/4=18 8Gbit DRAM chips per Rank.
but 32GB 2Rx8 uses 72/8=9 16Gbit chips per Rank, need one more address line which 1st gen scalable lacks.
What about 1rx4 would that work on 1st gen scaleable?