Does the Die Revision on identically spec'd Ram modules matter?

[Whizdumb]

So I’ve been trying to get to the bottom of a question for a little while now. Does Die Revision matter? Back in the early days of Ryzen I remember hearing all of the techtubers saying that Samsung “B” die ram was the best ram for Ryzen compatibility. Perhaps something in that revision was designed specifically to offer compatibility with the new processor at the time. All of that makes sense to me.

Now, I built an Epyc Rome server a little while ago and used Kingston 3200 DDR4 Ecc memory to do so. I only populated 4 dimms out of the 8 slots on my motherboard at the time. The ram I was using is specifically a Micron “E” revision of that particular module. Finding that same module now is darn near impossible. So now, it appears that there exists a same spec’d module in the Kingston line that just happens to be an “R” revision of the chips. Makes sense, as they sell through an older revision, a newer version of the module would find more prevelance on the market. All thing considered including rank, ecc, bus speed, Cas latency, chiplet layout, etc are all the same. So my questions are kind of general in regards to this…

1. It is generally assumed that a later revision of a chip is backwards compatible with a former Rev?
2. Assuming that they are relatively compatible, is there any real world performance penalty for combining them in the same system?
3. Does anyone here have any anecdotal evidence of this scenario either working fine or not working at all?

Feel free to have a discussion below about this topic so that it may serve as resource for anyone else who might come along with a similar question.

Thank you all.

[MetalizeYourBrain]

@Whizdumb

Cas latency

That’s the gotcha when new memory chips are used in the same series of memory modules: primary timings are exactly the same, but there are no informations on secondary and tertiary timings. Those are usually very specific to a memory DIE revision and might not be the same.
If there was a way to check if they’re exactly the same there won’t be a reason to be afraid of incompatibility of course.
Maybe buying four more sticks off Amazon, plugging them in (without the old one in) and checking if they match could be a good way to make sure if the two revisions are 100% compatible.