for those who hadn't done this for a while, PSA: motherboards these days have a RAM compatibility list on their product page, check it before overspending on RAM.
Did you try 6200/6000 for the kit? 6400 is up there for speeds that may not work on AM5 with synced controller and memory clocks without tuning it yourself, or working at all. Or is that 4 DIMMs
Anecdata: I just bought a used AM5 mobo and threw in this memory kit CMK64GX5M2B6400C32; hitting 6400 was as simple as turning on XMP and that's it.
That's a valuable PSA, but FYI it's been that way since the 80s. I've been bitten by compatibility issues at least once a decade since the 90s myself, and the answer from forums or support is always "did you check the compatibility table tho?".
[1] https://www.gskill.com/qvl/165/393/1665020366/F5-6000J3040G3...
CUDIMs should help a bit with those scaling tables due to having the clock redrivers, but we'll have to see to be certain how much.
Worth though. Much cheaper way to get a few extra percentage points than custom liquid cooling. And since every game where you would care about max FPS is bound by single threaded performance fast RAM is it.
That's a bit of an exaggeration. What matters are DIMMs per channel, and ranks per DIMM. Consumer systems have at most two memory slots per channel, so 2x 8GB modules installed correctly is just two separate instances of one DIMM per channel, and 4x48GB is two separate instances of two DIMMs per channel, with each module being dual-rank.
The best configurations for overclocking are supposed to be motherboards with only one memory slot per channel, so that when operating with one DIMM per channel there are no empty slots providing stubs of wiring that degrade signal integrity. But very few motherboards restrict themselves like this for the sake of memory overclocking.
Though I'd hope they'd finally start doing it considering the per DIMM capacities DDR5 brings (32 GB, with 64 GB planned), and most consumers really not going for capacities that'd require 2 DPC (DIMM per channel).
1 DPC should've been the default by now with the amount of 1 DPC and 2 DPC boards swapped, as it's just making things worse in the most common use case
From that angle I don't necessarily disagree with 4 channel boards being more common than 2 channel boards, even though I personally lean more towards a 2 channel board myself (well, depending how well CUDIMMS scale I may change my opinion).
The thing is that this is quickly becoming impossible, even with fairly low speeds like 6000 2 DPC is not achieveable in some cases, and consumers that are buying the 4 DIMM boards aren't particularly aware of it
Simplifying it to one vendor for the sake of conversations: for boards that explicitly target 9800X OCing users it's a bit silly to see 4 slots all the time but for the majority of boards that target the whole lineup it's not nearly as silly. Same for the 9900/9950X class where a lot of the users might be intentionally looking for larger amounts of slow RAM for heavier applications, not necessarily the absolute best bandwidth or latency the processor can manage.
I'd argue that whatever JEDEC specs intel/AMD puts up are mostly irrelevant to the reality of things, and the upgrade minded people won't be limiting speeds because of their speculative future scenario. This only leaves people who are on a very constrained budget and can't buy all the RAM at once. And they could buy a single 16GB stick and then buy another one later on when necessary. The losses from only using one channel aren't going to be as pronounced as on DDR4 either because of the 8GB's halved bangrkups and DDR5's internal channel split.
> Same for the 9900/9950X class where a lot of the users might be intentionally looking for larger amounts of slow RAM for heavier applications, not necessarily the absolute best bandwidth or latency the processor can manage.
I think DDR5 changes things up a bit here as 64GB is currently easily used and is enough for most, even heavier, workloads. Like for example for HN's audience some programming without worrying about memory being eaten up outside some more extreme cases. I agree that there's still a lot of people who'd need the ram even accounting for that, but they don't exactly need 80% of boards to have 4 slots
Or, perhaps stated differently, other than enthusiasts purchasing the best binned low density RAM who else has what practical gains by general consumer boards having fewer slots?
Same with "64 GB being easily used", true or not it's still not the capacities most are buying in new builds (32 seems to be the new common target for gamers, with 16 being the new minimum there, for example)
The other part of 2 DIMM boards is the trace lengths can be that much shorter (they need to be the same length so fewer slots means less max length to match to).