AMD Epyc 7451 Memory population question

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mirol

Member
Jan 6, 2018
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Hi I just ordered 2 Epyc 7451 and SuperMicro H11DSi-NT for it my question as I got 8x32GB 2133Mhz samsung ecc reg can I put another 8x8gb to populate full 8 channels or they need to be same size ?If not they will be and downsides use 8 gb with 32 gb mems?
 

vanfawx

Active Member
Jan 4, 2015
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Vancouver, Canada
Shouldn't be a problem, though your speed will drop once you populate 2 DIMMs per channel, which will directly affect your performance as Epyc is very memory-speed sensitive.
 

mirol

Member
Jan 6, 2018
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Hi I meant 4x32gb for each cpus and another 4x8gb then each cpu will have 4x32GB and 4x8GB (that way every cpu got all 8 channales populated) and they all 2133mhz.It will slow cpu down alot if they are only 2133 Mhz speed?
 

alex_stief

Well-Known Member
May 31, 2016
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No, mixing sizes the way you intended is not a good idea. It might run, but you will definitely take a performance hit in addition to the memory only being 2133MT/s.
It works this way with 2 DIMMs per channel. But not with only one DIMM per channel, as you will have with 16 DIMMs total.
But honestly: you spent how much on the CPUs? 16x16GB DDR4-2933 RDIMM can be had for less than 1500$. DDR4-3200 is still a bit more expensive. Edit: nevermind, thought you had Epyc 7002.