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Guidelines for choosing the right Memory for Coffeelake?

Level 7
Hi everyone,

I am about to buy a Maximus X Formula and cant decide which memory to buy. I want very good performance, but have several questions:

-Is it easier to reach 4000MHz with 2 Dimms or a kit of 4 Dimms? Is the same principle valid for High density dual ranked sticks (16Gb sticks)?

-Starting with Skylake, people reported higher benchmark scores (XTU) with 4 Dimms in comparison to two sticks. There also seems to be a slight performance increase by going with Dual ranked Memory. Is this the Case for CFL as well?
Which setup delivers the best performance at the same Clock?

-Is it better to go with 4x8Gb Sticks or 2x16Gb for performance?

-Is it true, that G.Skill TridentZ RGB has worse OC Potential than regular Trident Z ram?

I am sure this Information will help a lot of people, maybe Raja can share his wisdom with us 🙂



Level 13
1) If you favor plug-and-play, I'd look for a memory kit rated no higher than DDR4-3600. All the boards should be able to do that in either 1DPC or 2DPC configs. Go higher and there are variables that come into play that may prevent you from achieving the rated frequency and timings. In those situations, it can be wiser to fall back to a lower operating point with tighter memory timings. Decide the compromises you're willing to accept before making a purchase.

2) Assuming one can attain the right timings and frequency, generally, having more ranks is better. However, the difference in real-world applications is negligible.

3) Yes, the RGB kits do exhibit lower headroom than their non-lit counterparts.

Tahnks for the information!

Can you give a recommandation whether it is better to go for 2x16gb Modules or 4x8 GB Modules?

Level 13
That's already answered in number two.

Sorry, I assumed that 4 single rank dimms behaved similar to 2 dual rank dimms.

Thanks for the clarification.

Sorry for being dense but it is still not clear to me. I understand that Z370 is a dual channel platform but most of the G.SKill 4-dimm kits that list every Asus Z370 board in their (G.Skill) QVL are listed as quad channel kits. I don't understand that. I have also asked over at and done some general Googling on 2-Dimm kits verses 4-Dimm kits and I get totally conflicting statements.

Many say that a 4-dimm kit puts more strain on the IMC. Others say that a 2-dimm kit is better, and you have the option to expand later, which violates the "Don't mix kits" rule of thumb. So can someone (Raja?) clarify, in little words for my little brain, if I would be better served going with a 4-Dimm kit like G.Skill F4-3200C14Q-32GTZ or a 2-Dimm kit like G.Skill F4-3200C14D-32GTZ.

My planned MOBO is a Hero WIFI AC


Level 13
Those kits are labelled quad channel because they are validated on the HEDT platforms, too. As for which config is easier to run, it depends on a variety of factors. The ASUS boards utilize T-Topology, which favors four-DIMM configurations. However, one has to account for the capabilities of the IMC, as there is significant variance between samples. That's why the safe rule of thumb is to opt for memory kits that are rated at least three ratios below the maximum frequency the motherboard is validated for. This generally allows one to use a two-DIMM or four-DIMM configuration without requiring lots of manual tuning. Obviously, if you opt for a lower speed kit, your chance of plug-and-play improves (unless the memory vendor is using lesser memory ICs and binning them too aggressively).

And yes, it isn't recommended to add more modules to a config, as XMP is configured and validated for a single kit only.

Thank you Raja. Everything you said makes sense to me.