Question Can I underclock DDR 4000 to 3600 until it is fully supported on an AMD system?

kjm782

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Dec 14, 2008
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I am in the process of building a new computer that will be used as a workstation to do large amounts of data processing. So, I need a lot of memory (128gb) and faster is better. I was finally able to get a 5950x off of AMD's web site and am planning on using this motherboard:

https://www.newegg.com/asrock-b550-steel-legend/p/N82E16813157937?Item=N82E16813157937

I am debating about whether or not to get DD4 3600 or 4000 memory. My understanding is that with the latest AGESA 1.2 that people can get their fclk to 2000 so that DDR4 4000 is supported but it isn't always stable, especially at reasonable timings. I am assuming that in the future updates may make it so that you can comfortably use 4000 ram. Could I buy that ram today and then underclock in the meantime? The price increase for 4000 vs 3600 doesn't seem to be that much.

G.Skill DDR4 3600 (PC4 28800) - $397.99 x 2 = $795.98
Timing 16-22-22-42
Voltage 1.45V
https://www.newegg.com/g-skill-64gb-288-pin-ddr4-sdram/p/N82E16820374066?Item=N82E16820374066

G.Skill DDR4 4000 (PC4 32000) - $409.99 x 2 = $819.98
Timing 18-22-22-42
Voltage 1.40V
https://www.newegg.com/g-skill-64gb-288-pin-ddr4-sdram/p/N82E16820374047?&quicklink=true

A few questions:
  1. If I underclock the 4000 to 3600 will I be able to reduce the timings to match the lower CAS latency of the 3600?
  2. Since the 4000 operates at a lower voltage does this mean that it will generate less heat? Would the voltage likely be even lower if it is underclocked?
  3. Is there anything wrong with these ram options and/or are there other sticks I should consider?
Thanks in advance for the help!
 

Darkbreeze

Retired Mod
Personally, I'd go with the 3600mhz CL16 kit. It has a lower true latency to begin with, and no chance of having to pay a latency penalty if your configuration won't run those sticks without uncoupling the infinity fabric. Plus, as you say, stability issues. Not worth the headache and probably slower in the long run anyhow.

Save the money.
 

BogdanH

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Sep 21, 2020
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I would get 3600 too: stability is crucial and actual speed difference between 4000 and 3600 isn't that big as it appears at first sight (because differences in timings).
 

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