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Robotic Chemist
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Discussion Starter · #1 · (Edited)
I recently purchased another pair of low timing B-die DIMMs from G.Skill and much to my surprise I can run stable at very low timings with four DIMMs in a Asus X570 Crosshair VIII Dark Hero with a 5950X.

I believe this board is daisy chained. The only change I needed to make with these was to relax tRCDWR from 8 to 9 and enable RttNom. Auto also set tRDRDDD to 5 instead of 4 and tWRWRDD to 7 instead of 6, and I haven't tried changing them.

Two packs of F4-3600C14-16GVKA.
2519396

It passes stability tests with VDIMM = 1.415V but I run it at 1.425V normally.

I thought the issue with four DIMMs was due to the extra DIMMs per channel more than the quality of the memory itself, but now I suppose some aspect of the memory can impact it significantly. I have been playing around with memory on Ryzen for a while and all the other kits I have tried needed higher timings for four DIMMs (F4-3600C14D-32GVK, F4-4000C16D-32GTZNA, F4-3600C16D-32GTZR). If I tuned two DIMMs and then plugged in two more it normally wouldn't even post, but this memory can post at the same settings, it just showed errors in testing with tRCDWR at 8 (I leave RttNom set to auto, so it did enable itself).

I have other systems I could put the memory in, but I might leave it in this system since I don't have to give up any measurable performance to run it. :confused:

This also changes my feelings on some advice I have given in the past. Very good memory might be more worth it for 4 DIMM configurations on Ryzen 5000 than I thought. Or is this very unlikely? :oops: :unsure:

(This is not intended as advice for casual builders. More worth it does not mean worth it. Chasing timings too hard is poor price/performance.)
 

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Iconoclast
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31,436 Posts
Board and firmware matter a lot here, but in my experience, most Ryzen 3000 and 5000 setups can take four DIMMs, even double sided ones, to the realistic 24/7 limit for 1:1:1, with only moderate trade-offs. GDM usually needs to be enabled, and even if it's possible to run GDM off, it usually requires 2T. Beyond that though, if two DIMMs can do it, four generally can too, at least until 1900MHz/3800MT/s or so. I'm pretty sure all of my boards have been daisy chain as well.

Beyond those speeds, I'm much less confident, but I also don't have any AM4 systems that can do beyond 1900 FCLK with unconditional stability, so I haven't spent much time seeing how far I can push memory beyond that.
 

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389 Posts
Gdm does help a lot. I use four sticks @cl14 3800 but on a gigabyte b550 with t topology. Without GDM, and set to 1t, but some of my timings like trc, tfaw, tras are all looser by a decent bit.

Trfc (ns) for me is something like 141

I'm thinking you have a really good IMC though. That vcore is very low. My 5800x would absolutely be unstable.

Mine will run 1966 fclk stable as far as I've tested. Was using too much voltage for my comfort, though. So I think my IMC is pretty decent.

I think topology does help, but of course dimm quality is a big factor. And maybe IMC to a lesser degree?
 
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