Zen 4 and memory speeds

[Surly]

New to Zen cpu's and have a question...

So I understand that currently the sweet spot for memory performance on Zen 4 is 6000mhz DDR5, with ramped up speeds beyond that not showing significant gains. I loosely understand this is related to the current infinity fabric implementation in the memory controller(?) of the cpu.

My question is: If I buy into the AM5 platform, say with a 670 based board with the intention of dropping in a new cpu in 3 or 4 or 5 years, should I buy the absolute fastest DDR5 now even though current cpus dont really take advantage but perhaps future gen cpus (zen5+) might have a higher baseline infinity fabric implementation?

hypothetical example: Buy a zen4 in the next 3-5 months with DDR5 somewhere in the realm of 8000 to 10000mhz capability. This speed wouldnt not be exploited by current gen Zen but might be with next gen?

Or is the memory performance more a byproduct of the actual motherboard/motherboard chipset?

 

[LukeTbk]

Always possible that regular DDR5 + much faster than what you can buy now in 3-4-5 year's if is worth it would be much cheaper than buying the fastest DDR5-7000 to 7600mhz kit right now.

Cheapest 2x16 7200 mhz on pcpart picker seem to be $385 USD, CL-32 6000 kit can be found for $220.

$165 before tax can buy you a 4600 DDR4 kit which is near top of the line now and maybe it will buy (adjusted for inflation) a 7600 kit of DDR-5 in 3-4 year's (which will be mid range versus the good latency 8400 mhz kits and maybe the 32 gig will be the 16 gig of now and 64 gig will have come down a lot). You spent the same, better time distribution, you have 2 kits of ram and your high end one is better.

i.e. even if the fastest speed end up worth it, does not mean that it would have made sense to buy it in 2022.

 

[Surly]

so am i at least correct in that the memory speed support is built into the cpu and not the motherboard/chipset? What im trying to avoid is being limited by the motherboard. The socket longevity is much less valuable if essentially need a new mother board and new memory in 3 or 4 years anyways...

 

[pitingres]

It's both, really. The CPU has the actual memory controller. The motherboard doesn't contribute any active circuitry; it does have the BIOS which contains all of the setup parameters for the CPU's controller. If the motherboard CPU-to-memory traces aren't ideal, that can hold back top speeds.

I've read about plenty of AM4 X370 owners who might have struggled to get 3000 MT/s with a first gen Ryzen and early BIOS, who can now run 3600 MT/s and up with BIOS improvements and later-gen CPU's. I think there's a good chance that today's AM5 boards will support speed improvements down the line.

With the current state of DDR5, if it were me, I'd buy (relatively) cheap memory today and hope for significant speed and latency improvements, for less money, in a year or two. Today's fastest retail DDR5 is expensive and still has IMO mediocre latency numbers.