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BIOS or user error on memory timings(XMP)

Mummy84
By Mummy84
in New Builds and Planning
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Go to solution Solved by porina,

AMD CPUs have a Gear Down Mode that is on in certain situations (higher clocked ram being one of them) that makes it round odd CL to the nearest slower even value. If you dig through the bios and turn off GDM, it should allow 19 to be used.

Posted

Hi,

I have run my PC now fine over the weekend and now i desided to enable X.M.P. profile in my BIOS.

System boots fine without errors on overclocking issues etc.. and runs fine.

exept all progs. allso BIOS says that XMP on my RAM is 19-20-20-40, but BIOS sets it to 20-20-20-40

If you then manualy go to set timing 19 is allready selected on CL but F10 results CL20 again.

 

What makes this intresting to me?

Well if i set timeings to 18-20-20-40 it realy sets it to it and boots fine ada64 rusn fine...

So my Q is. Is it normal that BIOS cant set (or that memory cant stay) on some middle CL timeings like in this case?

So rebeat:

20-20-20-40 is ok

19-20-20-40 isn't ok

18-20-20-40 is ok

 

System specs.

AMD Ryzen3700x (stock)

ASRock X570M Pro4

G.Skill Sinper x 3600MHz DDR4. F4-3600C19D-16GSXWB

Corsair RM650x

EVGA GTX1080

 

Sorry yeah user error at least on the posting place Sorry

Can users move own topics or dos it have to be moved by mod?

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AMD CPUs have a Gear Down Mode that is on in certain situations (higher clocked ram being one of them) that makes it round odd CL to the nearest slower even value. If you dig through the bios and turn off GDM, it should allow 19 to be used.

Main system: i9-7980XE, Asus X299 TUF mark 2, Noctua D15, Corsair Vengeance Pro 3200 3x 16GB 2R, RTX 3070, NZXT E850, GameMax Abyss, Samsung 980 Pro 2TB, Acer Predator XB241YU 24" 1440p 144Hz G-Sync + HP LP2475w 24" 1200p 60Hz wide gamut
Gaming laptop: Lenovo Legion 5, 5800H, RTX 3070, Kingston DDR4 3200C22 2x16GB 2Rx8, Kingston Fury Renegade 1TB + Crucial P1 1TB SSD, 165 Hz IPS 1080p G-Sync Compatible

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Ahh ok. So next down should be then CL16 and as my memory SPD is 2133MHz it did exept CL15 as it was at "low speed"?

Is this odd number rule to all timeings or only CL?

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Yes it only effects on tCL

On my ASRock MB. "Gear Down Mode" is under the same menu "DRAM Timing Configuration".

PS. if you disable GDM and test it and after that set it back to "Auto" and save it. Then it seem like it wil auto tune it with GDM disabled in maind.

at least main did and after very very very long boot it passed and what i did see was that my timings was 19-20-20-40 but CR was 2 and not 1 like before.

 

My point is if you have long boot after this change. Then dont run to take power off psu, as atleast main didn respond 1 power button push shutdown and it was doing testing even thoug it didn seam like it did anything.

 

Anyway Thanks for good info Porina!

Have a good day all!

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