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CPU temperature varies a lot with a h80i V2 cooler


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I have a couple months old PC bought through a company where I selected all parts. Related to this question should be:

  • Gigabyte Z590 UD AC motherboard
  • Intel i7 11700KF CPU
  • Corsair H80i V2 pump

I started looking into how the PC operates since, when gaming, the system gets quite hot. The first thing I realized was that the pump was not operating at full capacity since I can see that the fan is working like it does when the pc is idle.

Running the simplest Intel XTU benchmark worries me. Looking at XTU numbers:

  • Temperature varies between ~40 and ~80 degrees
  • Voltage varies between ~1.240 and ~1.460V
  • TDP varies between ~80 and ~125W

See the attached screenshot for reference (1 minute interval), where it can easily be seen the changes in temperature:

tLHOD.png.2ef0d7ed8192f038b3858477e3eb03f9.png

CPUID's HWMonitor shows similar changes in temperature.

I installed iCUE 4 only to find out that my pump isn't supported (the website says IT IS supported), and then found that I could use Corsair Link 4. Unfortunately, what I see in CL4 doesn't make sense to me:

image.png.f2916680f0384e115c45f97b78f59768.png

The temperature reported in CL4 is always ~38-40 degrees. Fan is always at 0rpm and Pump varies in the range of ~900-3000rpm depending on load. I have uninstalled and reinstalled CL4 and found no difference. I tried with iCUE v3 (last version that can be downloaded) and it shows very similar numbers to CL4.


It seems to me that there's something not working correctly, like if maybe the pump is not correctly connected?

Edited by cfrozendeath
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1 hour ago, cfrozendeath said:
  • Temperature varies between ~40 and ~80 degrees
  • Voltage varies between ~1.240 and ~1.460V

This is why your cpu temp is all over the map. 1.46v is a pretty high number, but not uncommon if you set a mild overclock with “auto voltage” and settings. The cooler is working or you would not be able to keep it at 80C under that kind of Vcore level. Voltage is dominant factor in your instant cpu temperature values. Cooler settings have a small effect on the end number, but there are some things to optimize. 
 

The builder packaged up an AIO that is several years out of production. It will work in CUE 3, but not in CUE 4. However, Link is just fine if you don’t have any other Corsair devices to consider. Newer KBs, mice, headsets, etc will not be recognized by the Link program that was discontinued 3.5 years ago.
 

It does show you a few things. The temperature listed is your coolant temp or H80i v2 temp. This is the value the cooler regulates with its fans. This is the baseline or minimum possible cpu temp. If your coolant is 38C, then the CPU will be 38C at 0v.  Heat passes both ways across the conductive plate and the coolant can warm the cpu if it picks up heat elsewhere. You are most interested in the change in coolant temperature. This is the measure of heat in vs heat out. 38C is a bit warm, but not uncommon for a 120mm frame AIO in Summer, especially if it’s rear mounted above the GPU. 
 

The H80i v2 gets its pump power from the motherboard while most AIO units now get their power via SATA. This means the MB control header where it is connected needs to be locked out at 100%/12v. How to do this varies by motherboard make. Asus uses the term Full Speed. Most will set to max when the fan control for that header is “disabled”. The “Quiet” speed in Link should put the pump around 1900 rpm. You are a bit low. 
 

It appears the builder connected the radiator fans directly to the MB. This is common with builders who want them to run on start up and typically won’t install specific software or profiles for the end user. The fans are probably racing around based on cpu activity/temperature. That’s not the role they play here. The cpu is cooled by conducting heat away via the cold plate on the pump. Now the heat is in the coolant stream. The fans help dissipate heat out of the radiator, but this is s slow and steady kind of job. You don’t need them to react the cpu temp. Raising the coolant temp requires continued cpu load. Short term blips to max Vcore like when launching a program have no effect on the coolant. I would move the fans to the pump’s controller do you can control them via the software. It will take a little time to figure out where you want them and diving into the bios to tweak is a nuisance. 
 

 

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Thanks @c-attack for your response, it's very informative.


I don't have any other Corsair product that requires me to use iCUE, so using CL is fine.

The BIOS is currently set to everything at its default level, the only OC is that the RAMs are 2133 and using XMP to get them at 3000. The CPU has quite a lot of voltage-related settings set to Auto, but I have no clue what to look for to make it more stable. When running a stress test, the CPU only varies between 4.7GHz and 5.0GHz (max turbo V3 speed), so I know that it's not a problem of turbo shutting down and starting up again.

When idle, on the BIOS, I get a temperature of ~38C which is consistent to the minimum you were telling me, and on Windows I get ~45C. The cooler is sitting on top of a XFX Radeon 6700XT (only a few cm apart) so that's likely the reason.

I will try to find the setting on the BIOS to make the pump work at 100%. Can you comment a bit more about what should I do with the fans please? I didn't quite get you.

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The first thing that you really need to do is to redo the pump so that it is installed correctly. Because right now, it is not.

The fans should be connected to the controller on the cooler.

From there, the header that the pump is connected to - usually the CPU Fan header - has to be set to 100%. That pump isn't getting the power that it needs to operate properly and this will cause variations in pump speed ... and eventually can lead to pump failure.

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Hey @DevBiker

I just opened up the PC, and from what I can see:

  • There are 2 cables going out of the CPU-side of the pump
    • The first one is connected to the CPU_FAN pins
    • The second one is split in 2 and connects to the 2 cables coming out of the pump fans
  • There is one more cable connected into the CPU-side of the pump (looks like a mini-USB without disconnecting it)
    • I cannot easily see where this is coming from. I'd need to take out quite a few cables to see, given how the PC was built. Let me know if you need me to do this.

I got into the BIOS and set the CPU_FAN to "FULL SPEED". The pump gets quite noisy while in the BIOS, but after getting to Windows it looks like it's going back to "quiet" mode. In CL, I set the Profile to Performance and the reported pump speed is 1700RPM with 1% CPU load.

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Leave the mini usb alone. That is what allows you to control the AIO and see it in the software. 
 

Are the fans really connected to the splitter from the pump?  They should not read zero rpm. If you’re shure they are connected, try swapping the two fan connectors 1-2. Could be a bad tachometer wire/pin on one fan. The H80i v2 only needs one fan to control and the other mimics it. 
 

That was the right thing to do with Cpu fan in the BIOS. However, that pump speed is to slow for quiet. What is the reported speed if you set the pump to performance?

 

Your voltage and temps are normal for a “stock” setting. The thing is the actual Intel default settings are usually overridden by MB specific instructions. I would leave this alone for now. Once you’ve verified all is well with the cooler, then you can start looking at overclock and usage guides should you wish to take control of the voltage. The MB and CPU’s priority is stability at all costs and that normally means a heavy hand with voltage. We are just now entering a period where the cpu/mb will make individual decisions based on cpu sample quality. 

Edited by c-attack
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So, @c-attack, I've just turned off the PC and switched the 2 fan connectors that go to the pump. It's still reading 0, although for one second it read 1980RPM right after opening CL4. 

As for the pump, while it is set to FULL Speed on the BIOS, on Windows I get:

  • Quiet mode: 820RPM
  • Performance mode: 1720RPM

I think there might be some driver issue here. I hear the pump at full speed if I let the PC in the BIOS menu, and right after Windows log in, the pump stops for the most part and it works with very low noise. 

While writing this, I have just found out that the fan shows the speed when I start a test. I'm attaching two videos for your reference:

At this point, I'm wondering if the jumps in voltage/temperature are only because of how the tuning test works, since I don't see that in the stress test

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OK, I think the BIOS setting for CPU Fan supplying power to the unit didn't take.  I caught the fans magically appearing and the pump speed shifting all over during the tuning test.  That's not supposed to happen and suggests that power is still being applied/removed based on CPU temp in the BIOS.  All the Corsair AIO units use a fixed, but selectable pump speed.  It should not be swinging around by 1000 rpm and the fans popping in/out are a sign the total voltage to the unit is being cut.  In effect, your MB is acting like a dimmer switch based on CPU temp.  You need to stop that.

 

I am not as familiar with Gigabyte boards, but something like "Full Speed" or "Disabled" should lock the controller at 100%.  You also can force it into PWM mode to make a constant 12v, but the disabled/full speed is better so the MB won't try and tune it like a fan.  

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Ok @c-attack, I think I'm getting there! The MB had already set "FULL Speed" for the CPU Fan. I just disabled that, selected Manual mode and set 100% speed at 0 degrees. The CPU temperature is a bit more stable now and this is what I see in CL4 with 2% CPU usage:

image.png.4557d11c66941844fb03f5c4f0ce778b.png

 

Fan is set to "Default" profile and Pump is set to "Performance". If set the fan to "Max", then it goes to ~3200RPM. Now I get a constant reading for the Fan too!

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The pump should stay around 2800-2900 on Performance and 1900-2000 on Quiet.  You can use either you wish with noise vs performance in mind.  

 

Now for the fans...  The coolant temperature values are going to be strange to you and an awful lot of your value is going to come from the GPU waste heat vs actual CPU wattage into the unit.  There is a 40C=100% line programmed into the preset curves, but 2700 rpm is too much to take for most people and no matter what, you can't reduce coolant below ambient temperature.  That means you are spinning your wheels for no reason.  

 

My suggestion is you set a fixed fan speed that is acceptable to you for noise before gaming.  There are too many other things in play with rear mount exhaust to expect it to follow any programmed curve.  Pick something you can stand.  There is not going to be a meaningful cooling difference between 1800 and 1500 rpm for the CPU, but it may be very noticeable for noise.  Over time, you will discover the normal range of coolant temp and will be able to make a more precise curve if you want it.  To that end, you can also improve the preset curve now.  I am trying to remember how to do custom curves in Link.  You may need to click on the fan RPM reading in the picture above and a pop up will show.  You can create a custom curve based on the quiet curve, but soften the top end so it does not run 2700 at 40C.  Push that out to 50C.  Anything more than 1800 rpm is not going to be helpful for CPU cooling in this configuration.  Make sure the sensor/control variable is set to H80i v2 Temp and not CPU temp.  

Edited by c-attack
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Thanks @c-attack for all the help. I will leave the fan in Quiet as 60% at 40C sounds about right, noise doesn't bother me too much (not with an HyperX Cloud 2 headset).

As a last question, I was thinking of changing the extremely cheap thermal paste the CPU has and put something better. There's a quality brand on Amazon with 15.7W/m.k performance. Do you think this could make any difference?

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In a best case scenario, you might get 1-3C on changing from a normal product to premium. The larger the CPU die and the higher the CPU wattage, the more likely this helps by a few degrees. So for an AMD 3600x, you don’t bother. For a Threadripper or high core Intel, it might be. Just keep in mind there are no miracles with this or we would all be using the more expensive brand. 

Edited by c-attack
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Are you tracking the room/case temperature in these comparisons?  If you have a CPU that idles at 35C and 30C coolant, then when the environment temperature increases +5C you'll see 40 and 35C and the same shift in the opposite direction if the room/case is 5C cooler.  Idle coolant temperature is going to be almost entirely based on local ambient temperature.  The CPU is only outputting 10-20W at idle and that's not going to move the coolant temp around.  

 

There are a lot of professional TIM tests out there done in strict testing conditions.  Those differences are small, but would not account for the change when going from old/poor dispersal to a better application of any product.   Either way, it is clear the cooler is not malfunctioning or showing decreasing performance.  

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