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Falloppium
Journeyman III
Journeyman III

32x4 128gb DDR4 for Ryzen 9 5900X: lower latency OR higher frequency?

Hello everybody. 

The title should be self explicative. I'm gonna pair the Ryzen 9 5900x with 128gb of DDR4 (4x32). I have found two options, both compatible with either of the two possible mobos I am going to get (CH VIII Dark Hero, or Aorus Master, x570 of course), according to their respective QQL lists:

  • Hyper X Fury 3200Mhz (HX432C16FB3K4/128) 4x 32GB - DS - 16-20-20-39
  • Hyper X Fury 3600Mhz (HX436C18FB3K4/128) 4x 32GB - DS - Micron - 18-22-22-39

My rig will be used for both video editing and gaming, with the occasional streaming and certainly lots of multi tasking.

Shall I go for higher frequency or lower latency? And would it be possible for you to explain why? 

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6 Replies
rurouni51
Adept II
Adept II

Re: 32x4 128gb DDR4 for Ryzen 9 5900X: lower latency OR higher frequency?

Hi Falloppium,

You can calculate the actual latency to compare.

Using the examples you provided to compare the CAS latency 16@3200 vs 18@3600, actual latency is 10ns for both.

Calculate by multiplying the CAS value with the clock cycle time.  E.g for the 3200MHz kit, the clock rate is actually 1600MHz because it's DDR RAM.  So you would calculate with 16 * (1 / 1600000000) or simply 16 / 1600000000 to give you 0.00000001 (10ns).

Likewise for the 3600MHz kit, 18 / 1800000000 = 0.00000001 (10ns).

This means both kits will have the same actual CAS latency (for delay sensitive workloads they will be the same, but the 3600MHz kit will have higher bandwidth (for throughput sensitive workloads, the 3600MHz kit will provide more GB/s)

elstaci
Esteemed Contributor III

Re: 32x4 128gb DDR4 for Ryzen 9 5900X: lower latency OR higher frequency?

Deleted my answer after checking the QVL list for both Motherboards.  I answered before on my Cellphone and was unable to check the QVL lists.

The Asus Motherboard both the 3200 & 3600 Mhz RAM is listed for 4 slots while the Gigabyte Aorus Master version 1.2 it only shows the 3600 Mhz as being compatible in 4 slots but not the 3200 Mhz. 

I do know for best performance that the sweet spot for the Ryzen 3xxx processor is 3600 Mhz for RAM Speed while the sweet spot for Ryzen 2xxx Processors is 3200 Mhz.

But I don't know the sweet spot for the new 5xxx Processors.

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colesdav
Esteemed Contributor III

Re: 32x4 128gb DDR4 for Ryzen 9 5900X: lower latency OR higher frequency?

I have asked when:

https://www.techpowerup.com/download/ryzen-dram-calculator/

DRAM Calculator for Ryzen v1.7.3 Latest May 14th, 2020. will be updated to support Zen 3 processors
.

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coyote
Adept I
Adept I

Re: 32x4 128gb DDR4 for Ryzen 9 5900X: lower latency OR higher frequency?

Thank you very much for this, rurouni51!

What workloads are delay vs. throughput sensitive?

I would guess that the former includes gaming (which I don't do).

I do productivity tasks mainly, such as audio editing and encoding. And voice recognition. I'm guessing I should lean towards throughput?

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rurouni51
Adept II
Adept II

Re: 32x4 128gb DDR4 for Ryzen 9 5900X: lower latency OR higher frequency?

Hi coyote,

I don't deal with those apps myself, so I couldn't suggest either way.  If you're looking at the original post as options for yourself, remember that 3600MHz CL16 has the same actual CAS latency as 3800MHz CL18.  So from a CAS latency perspective they will perform the same.  However the 3800MHz will have more throughput.  Also bear in mind that the CL rating is not the only rating that can impact latency.  E.g. the BIOS on my Gigabyte TRX40 MBD has over 30 parameters I can change that may impact memory performance in some way.

Also bear in mind that due to "manufacturing variances" the 3000/5000 series is only guaranteed to run at 3200MHz.  Anything above 3200MHz may not work or be stable and mean you have to run it at lower the the rated speed.  E.g. my 3900x isn't stable with 3600MHz CL16 as my kit is rated for, I run it at 3200MHz CL14.

coyote
Adept I
Adept I

Re: 32x4 128gb DDR4 for Ryzen 9 5900X: lower latency OR higher frequency?

As it happens I did find this thread because I'm looking at the same 3600 MHz kit the OP is (on the Dark Hero).

I have a feeling that most of my work will benefit from throughput (though not the voice recognition, I'm guessing it would benefit from low delay).

So I think I'll stick with my plan to get that 3600 MHz kit.

Very helpful for me, as a beginner, to hear that when you couldn't achieve the 3600 you were able to go with lower CAS instead.

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