DDR5 RDIMM compatibility - Epyc 9004; HMCG94AEBRA109N with HMCG94AEBQA109N compatibility question

Hi all,

Like I mentioned in previous post, first time server parts owner.

I purchased 6x HMCG94AEBRA109N (SK Hynix 64GB - pc5-38400) and then found + purchased another supposed 2x of that kit. However the seller has informed me it was a listing mistake and is actually HMCG94AEBQA109N (also SK Hynix 64GB - pc5-38400)

My question is given I acquired an Epyc 9004 cpu (and mobo), will these dimms be compatible or do I have to exactly match the P/N?

Cant see any datasheets but all the listed specs from 3rd party memory vendors seem to match exactly between the two part numbers.

Cheers,
Sprout

I wouldn’t want the HMCG94AEBQA modules because they are functionally inferior to the HMCG94AEBRA modules.
There’s still a chance that they might be compatible with your motherboard because alot of the hyperscalers decided to cheap out with RDIMMs and spec EC4 instead of EC8 so compatibility isn’t completely terrible.

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That is a very, very good point. Thank you for pointing this out, genuinely didn’t notice that it is EC4.

Do you happen to know where I might be able to find sk hynix datasheets more readily so that I validate if the parts might have a greater chance at being compatible?

It doesn’t look like SK Hynix has the datasheet for the 16Gb A-die memory up any more, but they do have the datasheet for the 16Gb M-die memory which is very similar unless you overclock.

They make it hard to link to though; but if you go here:
https://product.skhynix.com/products/dram/module/rdimm.go
and look at product “HMCG94MEBQA109N”, you should be able to pull up the datasheet

Thank you, would you expect A-die + M-die to be a shit show? I can see better prices for HMCG94MEBRA121N/HMCG94MEBRA109N etc

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Yes.
You should be safe mixing and matching modules that have different 4-digit suffixes though, since this only specifies the register chip and power management circuitry manufacturer, which are all effectively interchangeable.

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Amazing. To any future googlers that means:

  • HMCG94AEBRA109N
  • HMCG94AEBRA123N
  • HMCG94AEBRA108N
  • HMCG94AEBRA121N

Are all compatible, there are a few more variants but I cant see them on Ebay.

here’s a more exhaustive list (but not complete) of all the different suffixes SK Hynix uses: