# CPU Fan RPM spiking



## plark (Jun 12, 2020)

Hey guys, just built a new pc and the fan on the CPU keeps spiking:









I have the Coolermaster Masterliquid ML420L and a Ryzen 3700x. Not sure what's causing it to spike like this and if there is any way to prevent it from doing so. 

Here's my entire system specs:

CPU: AMD Ryzen 7 3700X 
GPU: Nvidia GTX 1660S (Super) 
RAM: G.SKILL F4 DDR4 3600 C18 2x8GB 
MBD: Asus TUF GAMING X570-PLUS (WI-FI)

Any feedback or help would be appreciated, thank you!


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## Bill_Bright (Jun 12, 2020)

What do you mean by "just" built a new PC? New PCs typically go through a period of erratic loads/demands as Windows and other programs get all their initial updates. 

Plus, did you see the maximum 65°C temp? That could correspond to the CPU speed spiking. In other words, it could be perfectly normal.


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## plark (Jun 12, 2020)

Bill_Bright said:


> What do you mean by "just" built a new PC? New PCs typically go through a period of erratic loads/demands as Windows and other programs get all their initial updates.
> 
> Plus, did you see the maximum 65°C temp? That could correspond to the CPU speed spiking. In other words, it could be perfectly normal.



Finished the build Weds evening. Maximum CPU 65 on NZXT app is 65? On the Ryzen Applications it’s 90. So I’m a bit confused on that statement? Can you clarify a little?


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## Bill_Bright (Jun 12, 2020)

I am saying when CPU temps go up, it is common for CPU fan speeds to increase in speed too. While 65°C may not be the maximum the CPU can tolerate, 65°C may be above some threshold set in the BIOS that triggers an increase in fan speed. 

You should not attempt to block this increase in fan speed until you are 100% certain it is not being triggered by an increase in CPU temperature.


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## plark (Jun 12, 2020)

Bill_Bright said:


> I am saying when CPU temps go up, it is common for CPU fan speeds to increase in speed too. While 65°C may not be the maximum the CPU can tolerate, 65°C may be above some threshold set in the BIOS that triggers an increase in fan speed.
> 
> You should not attempt to block this increase in fan speed until you are 100% certain it is not being triggered by an increase in CPU temperature.



gotcha. It seems like it is by my screenshots. I just didn’t know if that was how it was suppose to work opposed you a constant fan speed keeping it at 45-50 degrees opposed to it spiking 45-50 degrees and a burst from the game happens


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## Bill_Bright (Jun 12, 2020)

The load on any CPU can go from near 0% at idle, all the way up to 100% in just a few clock cycles. And there are over 3 billion clock cycles in a single second with most CPUs. And the CPU's heat can drop to near ambient (room) temperature at idle, to overheating almost as quickly - depending on those load values. The CPU fan needs to react quickly to ensure the CPU does not over heat, or cross some thermal protection threshold and throttle back in speed. 

I recommend you use a HW monitor to keep real-time tabs of your CPU temps. I use and recommend Core Temp for that. You should be able to hear your fan speed ramp up as your CPU temps increase - just remember the fan speed increase will be slightly delayed as temps increase much more quickly than fan speeds due to simple reaction times being slower for the mechanical device.


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## plark (Jun 12, 2020)

Nice program! That’s exactly what happens. Once it hits mid to high 50’s the fan kicks on faster.


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## oobymach (Jun 12, 2020)

You can manually set fan speed in bios if you're using mobo headers to power your fans. I'm using a noctua with 2 different fans on it and use bios to set manual speed for each. Also can you take a pic of your case and if possible show what you have setup for airflow ie intake and exhaust? 65 isn't bad but are you doing any stress testing or is this just ambient temps?


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## plark (Jun 12, 2020)

oobymach said:


> You can manually set fan speed in bios if you're using mobo headers to power your fans. I'm using a noctua with 2 different fans on it and use bios to set manual speed for each. Also can you take a pic of your case and if possible show what you have setup for airflow ie intake and exhaust? 65 isn't bad but are you doing any stress testing or is this just ambient temps?



These are just ambient temps. I have a Coolermaster ML240L Masterliquid.


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## holyprof (Jun 12, 2020)

With the Ryzen CPUs (i have R7 3700X), temps go up and down quite fast, so the fan follows. I had to set it to custom fan curve and set falloff to 1 second (was 0.1s) to avoid the constant up and down. The configuration is in BIOS or motherboard app, not in NZXT CAM. I have only case fans controlled by NZXT CAM of my H500i case.

Even with that, the CPU fan was still noisy (1500-2000 rpm), so I replaced the stock AMD Wraith Prism with a cheap CoolerMaster Hyper212 and it now runs at slightly lower temperature with fan speed of 700-800 rpm.

Edit: now I see you have water cooler. Adjust the fan speed to something a bit lower, or even better, build custom fan curve.


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## plark (Jun 12, 2020)

holyprof said:


> With the Ryzen CPUs (i have R7 3700X), temps go up and down quite fast, so the fan follows. I had to set it to custom fan curve and set falloff to 1 second (was 0.1s) to avoid the constant up and down. The configuration is in BIOS or motherboard app, not in NZXT CAM. I have only case fans controlled by NZXT CAM of my H500i case.
> 
> Even with that, the CPU fan was still noisy (1500-2000 rpm), so I replaced the stock AMD Wraith Prism with a cheap CoolerMaster Hyper212 and it now runs at slightly lower temperature with fan speed of 700-800 rpm.
> 
> Edit: now I see you have water cooler. Adjust the fan speed to something a bit lower, or even better, build custom fan curve.



Thank you for the information. Is there anyway you can assist me with this? I’ve never heard or done this before.


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## Bill_Bright (Jun 13, 2020)

plark said:


> Nice program! That’s exactly what happens. Once it hits mid to high 50’s the fan kicks on faster.


Which sounds perfectly normal to me. And there's nothing wrong or worrisome about temps in the 50s. And if it peaks at 65°C under heavy loads, I would not worry about that either. But if your peaks are much higher than 65°C, then I agree with oobymach and you might want to look at your case cooling to make sure it is setup correctly and you have a sufficient supply of cool air flowing through the case. 

Generally, with conventional cooling (fans), you look for a front-to-back flow of air through the case with front fans pulling cool air in, and rear fans exhausting heated air out. If you have bottom and/or blowhole (top) fans, they typically produce a bottom-to-top flow. You also want a slight over or positive pressure in the case. That is, you want a little more air being pulled in (hopefully through air filters) than air being pushed out. This little bit of positive pressure causes a little bit of air to be pushed out through all the other little cracks and crevices and ports instead of being sucked in (along with dust and crud). This little bit of positive pressure also ensures the vast majority of intake air is coming through the filters (if you case is - hopefully - so equipped). 

Note that some top mounted radiators use top mounted fans that pull in rather than exhaust out and that's fine AS LONG AS there is still a sufficient flow of cool air for the other [often overlooked ) heat-sensitive devices (RAM, chipset, drives, graphics solution, VRMs, etc.).

But remember, no fan and no amount of air flow can cool your electronics cooler than the ambient (room) temperature - even with water cooling. So if your room is hot, so will your electronics.


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