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3600 or 4000 MHz RAM for my Ryzen 3950X workstation?

I’m building my dream workstation / battlestation at the start of 2020. I’m getting the Aorus X570 Master with a Ryzen 3950X, and I’m struggling to pick between these 2 RAM kits:

Corsair CMK32GX4M4D3600C18 (3600 MHz C18)
G.Skill F4-4000C18Q-32GTZKW (4000 MHz C18)

The G.Skill kit is over twice the price of the Corsair one. It’s about 11% faster on paper (400 MHz) but I feel like I’ve heard that the infinity fabric on Ryzen CPUs downclocks after the RAM exceeds 3600 MHz (or something to that effect), meaning that the increased clock speed won’t necessarily result in an equivalent increase in RAM performance, and it could hurt stability. Could it even hurt performance?

I would really appreciate it if anyone could clarify this a bit for me.

Everything else being equal, does 4000 MHz make any significant difference over 3600 MHz on the Ryzen 3950X?

If you could pick a kit for free in this situation, would you go for the 3600 MHz kit or the 4000 MHz kit?

My use cases are games, both [email protected] and [email protected], streaming, compilation of large code bases, emulation, virtualization and video encoding.

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That is right on the money, you don’t want the IF clock decoupled. So go with 3600 at max. (Depending on amount of memory and number of sticks you might even have to take a slight step down from that.)


Here you can find ALL the answers to your question.
tl;dr You can balance RAM frequency with IF frequency and changing the RAM:IF rateo over 1800 is tricky. Also make sure to get RAM validated for your motherboard.
DRAM calculator can help you out dial in the best settings on primary and secondary timings.

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I just go for Samsung ECC memory, ECC is also helping to reduce the risk of memory-related crashes due to too high frequencies even if it is counter-intuitive…

  • 8 GB/module: Samsung DIMM 16GB, DDR4-2666, CL19-19-19, ECC (M391A2K43BB1-CTD)

  • 16 GB/module: Samsung DIMM 8GB, DDR4-2666, CL19-19-19, ECC (M391A1K43BB2-CTD)

  • 32 GB/module: Samsung DIMM 32GB, DDR4-2666, CL19-19-19, ECC (M391A4G43MB1-CTD)

Just give them 1.35 V, make sure there is a little air flow over them and clock them away. Anything above DDR4-3800 is more or less just for dick/vulva measuring, get the timings as tight as possible and keep IF clock 1:1 to memory frequency (1900 MHz for DDR4-3800, for example).

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Is desktop AM4 capable of using ECC RAM? I mean I know it will work in the boards but dose any actual error checking happen?

Yes, AM4 can use ECC (Multi-bit ECC), I’m using an ASRock X570 Taichi with a 3700X and 4 x 16 GB Samsung ECC [email protected] at the moment (next month I change the CPU to a 3950X to free the 3700X up for a different build).

I think every ASRock motherboard is capable of ECC, just check your intended motherboard’s technical specifications if Unbuffered ECC is listed anywhere, a few manufacturers cheap out and don’t design the motherboard’s layout with the extra DIMM traces that are needed for ECC to function.

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One exception: The APUs don’t work with ECC. Some claim “it should work” but it doesn’t.

Nothing to do with “claiming” something:

On the APU side only the “Pro” SKUs that scarecely hit the retail market support ECC, on the non-Pro Raven Ridge/Picasso APUs AMD pulled an Intel for some reason and actively disabled ECC on the CPU-side.

But the OP is talking about Zen 2/Matisse so no problem there if you go with a suitable motherboard.

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2933 is happening soon for ECC (note you can OC the 2666 easily to that speed as thats what i currently have)

Yes, I know and I’ve been using Samsung ECC UDIMMs for quite a while now without any issues - that’s why I’m recommending them to the OP. :slight_smile:

Wouldnt probably get them if your going 3950x maybe the 2933 when they come out, but with Zen2 target of 3600 for best not worth the loss if your aleady spending that kind of money for ECC when DDR4 doesnt really throw many errors to begin with

Yeah, it would be nice to have everything at once but I’m happy if I can get a 3950X at MSRP next week - the memory currently used is a few years old and a leftover from my previous Intel home vm box.

That memory’ll do until the 32 GB Samsung ECC DDR4-2666 UDIMMs are back on the market (currently sold-out in Europe) or maybe DDR4-2933 ones hit the shelves in the meantime.

But as always, since Samsung doesn’t bin the DRAM chips they use for their own-branded modules there is a chance to get DRAM that handles a lot more than the part number might suggest - the four 32 GB DDR4-2666 sticks I got so far are running without any voltage change at DDR4-3200 in my experimental X470D4U home server, on the X570 Taichi I’ll try to hit the maximum 1900 MHz Infinity Fabric clock with DDR4-3800 for the fun of it :slight_smile:

I am looking to go the same route except I have the G.Skill 3600MHz C18, but wondering if you had to install a bios/agisa update to get your Aorus X570 Master play with the 3950X?

Just waiting to for availability of the 3950X near me.

Yeah I’ve found a better 3600 MHz kit since I made this thread (G.Skill Trident Z Neo DDR4 3600MHz 4x8GB F4-3600C16Q-32GTZNC).

As far as I’m aware, the 3950X should work out-of-the-box on all X570 boards. I’m not buying this PC until around February 2020 though, so I can’t tell you for sure.

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Yeah, I’ve been picking parts up as the go on sale but probably not likely to get the 3950X till around January or February just because of the availability. None have been available in the city I live in since launch. It’s the last piece of the jigsaw I need now.

I got the G.SKILL Trident Z Neo (2 x 16GB) F4-3600C18D-32GTZN

Thanks for the tip, I went with 4x16GB 2666 DIMMs. Running them at 3333 Mhz C17 stable @ 1.362v (Samsung M391A2K43BB1). This is on an x570 Taichi & 3900x. cant get 3400 to post, but I’m ok with 3333. :slight_smile:


Thanks for sharing your experiences!

I’m on hold for >2666 MHz Samsung ECC UDIMMs that just don’t want to be introduced to the market :frowning:

Looking for a set of 4 or 8 of them, I want fast ECC for my server build.

Sharing a relevant post below. Kingston issued a product change which may mean some 3200 Mhz ECC modules will be in circulation.

ECC binned for 3200 MHz @ 1.2V