CPU clock drop when using 16*64 ram. I really dont understand why.

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sharonyue

New Member
Apr 20, 2022
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Hi guys, these days I run into a very strange problem. Previously I have 16*16RAM (3200) installed, everything runs fine. These days I install 16*64ram in my workstation. But the CPU clock sometimes drops by no reason (I am runing aida64 or other ANSYS CFX to use 100% CPU). I really dont understand why.

My settings are: 2*epyc 7502 CPU, h11dsi motherboard.

I tried all these OS settings, such as setting it as performance, I tried different BIOS settings, it does not solve the problem.
I installed win server2019, I re-install win10, CPU clock drops.
I changed to another CPU, such as 2*7642, CPU clock drops as well.
I changed to another motherboard, the clock drops sometime.
I changed to another 16*64 RAM (2400), clock drops again.
I changed other Fans, it drops as well.
I also tried install one CPU in one socket, with 8*64RAM, it drops.

Almost I changed all the things, as long as I install 64RAM install, CPU clocks drops. Only when I install one 64RAM, CPU clock does not drop.

I really dont understand why. Anyone can help me ?
 

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RolloZ170

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Apr 24, 2016
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just a guess: the Memory controller needs power, this power is removed from the overall TDP.
on heavy RAM access there is maybe not much TDP left for the cores...just a guess.
 
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sharonyue

New Member
Apr 20, 2022
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RolloZ170 said:
just a guess: the Memory controller needs power, this power is removed from the overall TDP.
on heavy RAM access there is maybe not much TDP left for the cores...just a guess.
Click to expand...
Hi Rollo,

I tried Ubuntu, it does not drop. But I tried every settings in Windows, it drops all the time. Now I quit debugging this... Too time consuming.
 
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sharonyue

New Member
Apr 20, 2022
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uldise said:
are you adjusted power management setting in Windows to High performance? it's default to Balanced..
Click to expand...
Yeah, Indeed, I tried every different settings in windows, including "register" "high performance" and others, I cannot remember them clearly. Very wired.

In windows, only when I change another 16*16 RAM, it goes back to normal. At the beginning, I suspect the problem comes from those 3200/64G ram. I changed another 64g/2400 RAM, it droped as well.
 
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sharonyue

New Member
Apr 20, 2022
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tinfoil3d said:
And everything still works fine in linux?
Click to expand...
Yeah, everything works fine in linux.
Really dont know why. This how it looks.
It should be noted that it does not come from the fan, overheating...
Right now this problem can be only handled by replaing 16*16 or 16*8 RAM.

Wired
ts.jpg
 
tinfoil3d

tinfoil3d

QSFP28
May 11, 2020
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Look. Just to rule out hw issue, did you... try another PSU? I mean, sure it's strange but I have experience with a ghost-faulty PSU a decade + ago, where windows was freezing up randomly but it only happened like 1-2 times a year in linux under somewhat same loads. The issue was PSU after all. I thought it was GPU but when replacing it didn't solve anything I replaced PSU and magically all was fine again. So windows in the past and probably now has somewhat different power loads than linux, and that can cause PSU problems to show up.
 
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sharonyue

New Member
Apr 20, 2022
27
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tinfoil3d said:
Look. Just to rule out hw issue, did you... try another PSU? I mean, sure it's strange but I have experience with a ghost-faulty PSU a decade + ago, where windows was freezing up randomly but it only happened like 1-2 times a year in linux under somewhat same loads. The issue was PSU after all. I thought it was GPU but when replacing it didn't solve anything I replaced PSU and magically all was fine again. So windows in the past and probably now has somewhat different power loads than linux, and that can cause PSU problems to show up.
Click to expand...
Thanks bro. I forgot to mention, I tried to replace the PSU. Same problem... I install servers for a living, I have a lot of things that I can replace. I replaced everything... The only thing that I cannot replace is the motherboard's model, h11dsi. I have a lot of motherboards, but same model.
 
tinfoil3d

tinfoil3d

QSFP28
May 11, 2020
882
407
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Japan
Well then, try putting everything into another similar board if you say you have other h11dsi. h11dsi and ssl are around for some time, back when EPYCs were announced I wanted to get a single socket one but vendor told me they had some issues(he didn't say what issues exactly) with them and were holding further shipments, which resulted me in looking for alt options, which right now is asrock rack epycd8-2t.
But if you establish that it's not a hw issue, then i have no idea because i don't run windows anywhere on such high-performing machines.
Another suggestion may be to reset all bios settings to defaults and see how that goes. I understand we all tweak bios settings but that may be exactly the reason for misbehaviour in this case. Then try changing values one by one to the necessary ones and reboot and re-test. Step by step.
 
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RolloZ170

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Apr 24, 2016
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sharonyue said:
nope, I run ANSYS CFX in linux. This is a CFD software, it can also use 100% CPU. Clock does not drop.
I also run ANSYS CFX in win, CPU clock drops.
Click to expand...
what is the power on the wall ?
compare the power draw: linux vs windows.
 
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sharonyue

New Member
Apr 20, 2022
27
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Im back, it looks not the problam of RAM. Since yesterday my workstation also has this problem. and it happens much often. Please see the image. It has 16*8G RAM. I really dont know why.

微信图片_20220604084535.jpg
 
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