did they also make a compatible motherboard ? because I can't get mine to go past 4800Mhz when my RAM is rated for 6400Mhz with AM5 CPU.
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.
The motherboard QVLs aren't particularly useful, the higher tier kits can often just not work as they're currently more often than not limited by the CPU memory controller quality instead of purely motherboard or RAM ICs.
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
> PSA: motherboards these days have a RAM compatibility list on their product page, check it before overspending on RAM.
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?".
Some memory manufacturers have lists of motherboards compatible with a given memory kit. E.g. I checked that my motherboard was listed in [1] before buying the memory, and everything worked effortlessly together with EXPO on.
I had similar issue with my 3950x
I had stability issues with 3600MT, so I optimized clicks instead
(I loaded XMP profile and then changed clock to lower value before tightening clocks with memtest runs in between)
What people often don't realize that dimm quality allows you to get lower absolute time before data is available for system. So when you lower clocks, you don't need to wait that many cycles for the data.
In that case you might not get that much bandwidth that you would have originally, but you can get the same or similar latency
also changing order of dimms on board can somehow alter how low you can get (I have 4 dimms and swapping 2 on the same channel improved significantly clocks that I was able to achieve - no idea why)
More than the specific list of which RAM is compatible check the table of how many slots/GB is supported at which speed. 1x 8 GB DIMM is a lot easier to drive than 4x 48 for example. Also keep in mind a lot of it depends more on the CPU than the motherboard itself, though both play a part, and the QVL should be a "safe bet". Particularly if you're willing to throw a bit of extra voltage at the RAM.
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.
> 1x 8 GB DIMM is a lot easier to drive than 4x 48 for example.
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.
4x 8 GB is still a lot easier to drive at high speed than 4x 48 GB, but yes, one factor in the above comparison is indeed the number of DIMMs per channel. Ranks per DIMM is definitely a factor as well, though on large capacity DIMMs that tends to be a one sided story. Another factor in the rabbit hole is banks, tying it all back.
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).
> 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
A lot of consumers care more about either of total capacity or the concept of "I can just double my cheap RAM later" than care about ~10% differences in RAM clock speed. The latter is for those that really know what they're doing to eek out a couple more percentage points in benchmarks or non-consumer use cases, the former appeal to both budget users and prosumers alike (just not OC enthusiasts).
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
Even 6000 MHz isn't necessarily "cheap low speed" RAM though, it's still a 400 MHz OC on Zen 5/14th Gen. ~$44 gets you 2x8 GB 4800 but it's ~$63 to start with 2x8 GB 6000.
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.
> Even 6000 MHz isn't necessarily "cheap low speed" RAM though, it's still a 400 MHz OC on Zen 5/14th Gen. ~$44 gets you 2x8 GB 4800 but it's ~$63 to start with 2x8 GB 6000.
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
According to PCPartPicker, 2x48GB kits at DDR5-5200 are currently the cheapest DDR5 on a $/GB basis, so you really need to have a workload requiring more than 96GB of RAM to justify having more than two DIMM slots. That's pretty solidly into workstation territory.
Is it far off in terms of $/GB in a normal user starting with 2x24 GB 5200 at ~half the up front cost while still being able to upgrade 4 years later, if needed, when memory is even cheaper and RAM requirements are higher versus all that pro/con difference against being able to run 2 high end DIMMs at 6400 instead of 6000 or similar difference by limiting the number of slots on the board. Again, I still think this makes plenty of sense for boards focused on OC enthusiast but paying more for the 400 MHz on a tradeoff of not being able to expand just doesn't seem particularly worth it on normal boards for normal users.
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?
People on HN can probably be assumed to want to go past JEDEC 2x48 GB RAM every time, I, again, wouldn't argue what HN should do as what the average consumer should be expected to do though. Much like I don't expect to recommend the average HN reader get the 6 core variant but it doesn't mean it's not as popular to general consumers due to price.
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)
And they’re often not stable even with the given XMP profiles. All of my XMP profiles throw errors and require backing off speed by a few hundred hertz to be stable.
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.
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.