Comment by wtallis

Comment by wtallis 2 days ago

> 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.

zamadatix 2 days ago

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).

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Numerlor 2 days ago

> 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

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zamadatix a day ago

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).

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- Numerlor a day ago
  
  > I can just double my cheap RAM later
  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
  
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  zamadatix a day ago
  
  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.
  
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