What's the current state of affairs with 4 DIMMs of DDR5 at the same time?

[Soapy1234]

Pretty much as the title says.  I'm planning an upgrade for my recording/mixing/orchestrating PC, and because of the samples I use for orchestrating, I need all the RAM I can get.  So I know that they have 48GB DIMMs out these days, and four of them would bring me to 192GB RAM (which I would actually use all of, if not most of).  That said, I remember as recently as last year that there were issues with DDR5 DIMMs slowing down considerably if all four slots are populated, and I wasn't sure if that's still the case or if that's been solved since then.

 

Anyone have any insights?

[OddOod]

AFAIK it's unstable as heck and fixes aren't really expected until next chipset generation. But I'm not closely following that story

[-rascal-]

It looks like 4x DIMMs is still a bit of a hassle, as of... 2 months ago.

Some people are having some luck with 4x DIMMs, but the speed is significantly reduced.

 

I agree with @OddOod, it likely needs to be fixed/improved within the CPU Integrated Memory Controller (IMC) itself.

[Somerandomtechyboi]

quad rank ddr5 is a complete dumpster fire and you should avoid if possible

 

does your workload happen to rely on singlecore or no? if not you can go buy some cheap zen2 epyc and get 512gb+ ddr4 for relatively cheap

[Soapy1234]

32 minutes ago, Somerandomtechyboi said:

quad rank ddr5 is a complete dumpster fire and you should avoid if possible

 

does your workload happen to rely on singlecore or no? if not you can go buy some cheap zen2 epyc and get 512gb+ ddr4 for relatively cheap

Unfortunately yes.  It would require both fast single core speeds for recording/mixing audio and high core counts for the samples--because that one tends to scale a lot better thanks to the program I use that houses them, Vienna Ensemble Pro.  Put another way, something like a 7950x would be ideal, but possibly overkill as far as core count, but the samples I use are HEAVY, so I imagine they'll take whatever I throw at them.

 

1 hour ago, -rascal- said:

It looks like 4x DIMMs is still a bit of a hassle, as of... 2 months ago.

Some people are having some luck with 4x DIMMs, but the speed is significantly reduced.

 

I agree with @OddOod, it likely needs to be fixed/improved within the CPU Integrated Memory Controller (IMC) itself.

Good to know it's still an issue.  I'll keep an eye on it when the next gen of chipsets are announced and hit the market.  Might even wait for the next CPU generation, though I kind of was planning on doing that anyway.

[Somerandomtechyboi]

2 minutes ago, Soapy1234 said:

Good to know it's still an issue.  I'll keep an eye on it when the next gen of chipsets are announced and hit the market.  Might even wait for the next CPU generation, though I kind of was planning on doing that anyway.

next gen amd is apparently gonna use the same i/o die with the same imc afaik, dunno about intel but considering that its been a few years and imcs are still dogshit for anything thats quad rank and/or quad stick yeah might have to wait another 2 or 3 gens

 

however amd does have apus which have better imcs so maybe those would be able to run quad rank at decent speeds or atleast next gen if current gen still has the same quad rank issues, just that youll be stuck with 8 cores

[RONOTHAN##]

44 minutes ago, Soapy1234 said:

I remember as recently as last year that there were issues with DDR5 DIMMS slowing down considerably if all four slots are populated, and I wasn't sure if that's still the case or if that's been solved since then.

It's still a problem, the degree of which depends on what CPU you're running, and odds are it will remain an issue for the lifespan of DDR5. It isn't really 4 DIMMs themselves that cause the slowdowns, there are some people who have legitimately gotten 6400MT/s+ working on 4 DIMM configurations (there's one I'm aware of who got 7200MT/s to work, though their stress testing was IMO inadequate at best so I don't exactly trust that it actually works), the issue is that 128GB or 192GB of RAM is going to be quad rank. 

 

Memory controllers in general struggle with more memory ranks. DDR3 wasn't that bad, maybe 100MT/s going from single to dual, and DDR4 something like 3333 vs. 3000MT/s on early platforms (this gap widened a bit towards the end, 11th gen was something like 4533 single rank vs. 5333MT/s dual rank at the end of the line for absolute best case scenarios), and DDR5 is even worse, going from something like 7200 to 6400MT/s for dual rank vs. single rank. Going to quad rank, or effectively double the amount of memory chips the memory controller needs to give commands to, is even worse, and DDR5 memory controllers struggle hard. On Intel, the best you can possibly hope for with quite a bit of effort is 5600MT/s, and you'll usually get stuck at 4400-4800 depending on how good your CPU is. On AMD, it's a bit worse, with 5200 being the absolute best CPUs and a ton of effort tuning things like termination settings and 4000-4400 being where most people are stuck at the maximum. It will likely take a complete memory controller redesign to get any sort of improvement, so either Zen 5 or LGA 1851 if it's even possible to improve at all. 

 

 

If you really need 192GB of RAM, you don't have an option, and running out of memory is going to be significantly worse than running with snail speed RAM. That said, if you can maybe get by with 128GB of RAM, 64GB DIMMs should be making it to the consumer market sometime later this year and should actually function at speeds of 6000+. 

[Soapy1234]

On 5/2/2024 at 9:24 PM, RONOTHAN## said:

It's still a problem, the degree of which depends on what CPU you're running, and odds are it will remain an issue for the lifespan of DDR5. It isn't really 4 DIMMs themselves that cause the slowdowns, there are some people who have legitimately gotten 6400MT/s+ working on 4 DIMM configurations (there's one I'm aware of who got 7200MT/s to work, though their stress testing was IMO inadequate at best so I don't exactly trust that it actually works), the issue is that 128GB or 192GB of RAM is going to be quad rank. 

 

Memory controllers in general struggle with more memory ranks. DDR3 wasn't that bad, maybe 100MT/s going from single to dual, and DDR4 something like 3333 vs. 3000MT/s on early platforms (this gap widened a bit towards the end, 11th gen was something like 4533 single rank vs. 5333MT/s dual rank at the end of the line for absolute best case scenarios), and DDR5 is even worse, going from something like 7200 to 6400MT/s for dual rank vs. single rank. Going to quad rank, or effectively double the amount of memory chips the memory controller needs to give commands to, is even worse, and DDR5 memory controllers struggle hard. On Intel, the best you can possibly hope for with quite a bit of effort is 5600MT/s, and you'll usually get stuck at 4400-4800 depending on how good your CPU is. On AMD, it's a bit worse, with 5200 being the absolute best CPUs and a ton of effort tuning things like termination settings and 4000-4400 being where most people are stuck at the maximum. It will likely take a complete memory controller redesign to get any sort of improvement, so either Zen 5 or LGA 1851 if it's even possible to improve at all. 

 

 

If you really need 192GB of RAM, you don't have an option, and running out of memory is going to be significantly worse than running with snail speed RAM. That said, if you can maybe get by with 128GB of RAM, 64GB DIMMs should be making it to the consumer market sometime later this year and should actually function at speeds of 6000+. 

Good to know about that last bit, but either way that'll be an issue (cause for my workload, 256GB RAM would be even better--like I said, they'll take what they can get, and while I'm not doing ANYTHING to the scale of say a Neil Parfitt who started out with 384GB RAM on his Intel Mac Pro and has since doubled that, it's still an issue).

Now with the program Neil and I both use to host samples, Vienna Ensemble Pro, it actually allows you to actually use multiple computers to host samples as essentially server farms, which can scale up as you need them (such as Hans Zimmer with his 35 or Junkie XL with I think 10).  What that means is I'm wondering if it would be wiser to just build a new DDR4 machine with Zen 3 and 128GB RAM if it's going to possibly be ANOTHER few years before they get the quad-rank issue under control--and that assumes we don't run into a situation where motherboards just start soldering the RAM on directly, which Emily from LTT said in a video 2 years back that was eventually going to happen for desktop PCs.

Something like a 5950x is still pretty insane for any kind of sample hosting, and considering they're going for cheaper and cheaper as time goes on, that could be an idea, and then buying another 128GB of DDR4 (or doing a parallel build upgrading my main studio PC come Zen 5, which really just needs 128+GB RAM for sample hosting locally).

What does the hive mind think?

[RONOTHAN##]

1 hour ago, Soapy1234 said:

if it's going to possibly be ANOTHER few years before they get the quad-rank issue under control--and that assumes we don't run into a situation where motherboards just start soldering the RAM on directly, which Emily from LTT said in a video 2 years back that was eventually going to happen for desktop PCs.

So I'd be surprised if we get soldered RAM before the introduction of DDR6/QDR1, that's probably not something to be too worried about. As for quad rank issues, they very well might never be solved. DDR5 has a ton of bank groups on it, and the more bank groups there are, the harder it is to control at high frequencies. In terms of just bank groups, dual rank DDR5 is about the same as quad rank DDR4, so it's understandably hard for the memory controller to control. 

 

1 hour ago, Soapy1234 said:

I'm wondering if it would be wiser to just build a new DDR4 machine with Zen 3 and 128GB RAM

I don't really see the point in this if you could just do 128GB of DDR5 with a 2x64GB configuration once they're released later this year. Hopefully they're coming out soon since Kingston teased them late December 2023, but we won't know until they finally hit store shelves. If you can wait a month or so to see if they will launch and you can just do that and possibly upgrade to 256GB if it turns out you need more RAM and damn the speed, I would since if you went Zen 3 you would be locked to 128GB at the maximum no matter what. 

[Soapy1234]

3 hours ago, RONOTHAN## said:

So I'd be surprised if we get soldered RAM before the introduction of DDR6/QDR1, that's probably not something to be too worried about. As for quad rank issues, they very well might never be solved. DDR5 has a ton of bank groups on it, and the more bank groups there are, the harder it is to control at high frequencies. In terms of just bank groups, dual rank DDR5 is about the same as quad rank DDR4, so it's understandably hard for the memory controller to control. 

 

I don't really see the point in this if you could just do 128GB of DDR5 with a 2x64GB configuration once they're released later this year. Hopefully they're coming out soon since Kingston teased them late December 2023, but we won't know until they finally hit store shelves. If you can wait a month or so to see if they will launch and you can just do that and possibly upgrade to 256GB if it turns out you need more RAM and damn the speed, I would since if you went Zen 3 you would be locked to 128GB at the maximum no matter what. 

Fair enough.  Question is how much of a hit would it be on my potential machine for what I'm trying to do.  I'll keep an eye on the next chipset and see if it gets solved, but I'm not counting on anything.  Obviously I also want to wait for 64GB DIMMs, and hope AMD's next chipset is compatible with said DIMMs.  Would probably go AMD because electricity is pretty expensive where I live, not to mention the stability issues from the most recent Intel gen that popped up recently after those chips were being abused (through normal use from my understanding) for so long.  And that says nothing about how the radiators in my building turn every room into a sauna if given the opportunity.