What actually impacts memory capabilities on am4 boards if memory controller is in cpu?

[spectatorx]

This thread is just pure asking for completing my theoretical knowledge about ryzen and am4 platform.

One of basic elements of ryzen architecture is that memory controller is located in cpu. From practical perspective we see big differences on how memory performs between various motherboards models and bios versions. If memory controller is located in cpu then there should be no difference in how memory is handled between various motherboards. On the other hand there are differences in motherboards designs like daisy-chain vs t-topology, various solutions for memory VRM and so on. I understand for oc better vrm means more possibilities to provide power for higher and stable oc, daisychain vs t-topology to improve compatibility with 4 sticks in all 4 slots. But there were basic compatibility issues with specific sticks/kits which were ironed out with bios updates so motherboards were able to support these sticks and kits which before update were working bad or even not working at all.

Knowing all that i'm scratching my head over this dilemma wondering why differences in memory support can be that wide. I do not even mean memory oc but things like basic compatibility of specific sticks, kits and their rated frequencies. If memory controller is in cpu then why motherboard model and bios version can make such huge difference?

 

[TheoneandonlyMrK]

Well the motherboard vendor type and bios model have a direct effect on what ageesa version your CPU will run using, its a bios file that controls the microcode that runs in the cou and can be updated to allow better compatibility/ support or stability in various ways.
Also on ryzen the interconnected fabric(infinity fabric) that connects the cores and everything else , also runs at the memory clock speed so it too Adds to an overclocks performance.

 

[tabascosauz]

Aside from board design and board layers, Ryzen IMC is simply pretty bad at being consistent. As we all know, Infinity Fabric places a cap on memory speeds as well.

There's too many factors in the mix. You have 3 generations of CPUs and 2 generations of APUs sharing the same socket with near-full backwards compatibility, yet all 3 generations are at different levels in terms of IMC capability and consistency. 3 generations' worth of different chipsets, with boards of varying quality, topology, memory VRM, and numbers of layers all over the place.

You have board vendors making BIOS updates to make a 3700X work on X370 boards, but X370 boards were designed for a 1800X. What Zen 2 IMC is capable of is not reflective of what Zen IMC was capable of. I think you can see where this is going.

XMP also originated as an Intel technology. Our DIMMs do support "XMP 2.0", but I suspect the fact it runs less than impeccably on AMD isn't exactly irrelevant to the fact that the vast majority of these DIMMs advertise Intel platform compatibility instead of AMD. From what I have seen, B-die kits represent the only exceptions to that rule.

Lastly, as is best represented by the existence and demands of IF, Zen is not the same as Core. There's few direct comparisons to be made.

 

[Mussels]

the automatic settings for RAM timings are controlled by the board, thats about it and only really affects overclocking outside JEDEC standards.

beyond that at the extreme ends, i'm sure theres quality difference for voltages, EMI, etc.