Question Help me to understand how cooling and cooling monitoring works ?

[omarCG]

I have lenovo gaming laptop 3, ryzen 5 5600H, RTX 3060. and I just found out there is no way you can neither monitor nor control your fan. Long story short, when i was trying to disconnect and reconnect the fans I accidently cut the CPU fan connector. Thankfully I got it fixed and working again but now I have few questions:

1-how does the laptop monitor cpu temperature, is it through fans or does the cpu has a dedicated sensor for temperature? because when I tried running the laptop without the cpu fan it ddnt show much of a difference except under high loads (low loads stayed around 40 - 45 c)

2-for some reason I don't feel the fan is as powerful as it used to be, I got the connector replaced it's a 4 pin connector with what I guess is + and - electrodes, a ground and a sensor pin. it's working alright but not as powerful, what could be the cause of that? could it be the sensor pin ? what its the role of the sensor pin anyway is it to change the fan speed ?

 

[Lutfij]

The BIOS on the motherboard helps manage the fans and the fan's curve(the speed at which it should rotate when it hits a point on a temperature curve/graph).

You could try and see if your laptop is pending any BIOS updates. As for your point about not being able to manage the fan in your laptop, might want to give this a read.

 

[hotaru.hino]

1-how does the laptop monitor cpu temperature, is it through fans or does the cpu has a dedicated sensor for temperature? because when I tried running the laptop without the cpu fan it ddnt show much of a difference except under high loads (low loads stayed around 40 - 45 c)

Modern CPUs have an array of thermal sensors. However they typically only report one or two values from this.

2-for some reason I don't feel the fan is as powerful as it used to be, I got the connector replaced it's a 4 pin connector with what I guess is + and - electrodes, a ground and a sensor pin. it's working alright but not as powerful, what could be the cause of that? could it be the sensor pin ? what its the role of the sensor pin anyway is it to change the fan speed ?

Assuming the laptop is using the same 4-pin configuration as desktop fans, the sense pin is for telling the computer how fast the fan is spinning. What changes the fan speed itself on a 4-pin configuration is the PWM signal, which has something called a "duty cycle" that determines how fast the fan should spin.

So one pin actually controls the speed, the other is to make sure the fan is actually working.

 

[Paperdoc]

In any computer the CPU chip has its own temperature sensor (in some CPU's, more than one) built in and the mobo uses that to monitor the CPU internal temp. SOME systems also use a second CPU temp sensor built into the chip socket on the mobo. For mobo temperatures there is a separate sensor on the mobo.

A 4-pin fan has 4 wires to it:
Pin #1 - Ground
Pin #2 - fixed +12 VDC power supply
Pin #3 - Speed signal
Pin #4 - PWM signal.

The speed signal on Pin #3 is generated by the fan and sent back to the mobo on this line. It consists of pulses 5 VDC high at a rate of 2 pulses per fan revolution. The mobo header just counts those to measure fan speed. Although we talk of "speed control", what this really is, is a TEMPERATURE control system. That is, the target is TEMPERATURE (for the CPU, the temp inside that chip), and the automatic control system manipulates the signal to the fan to ensure that target is met. The system does not care what the speed is - it does not even use the speed signal for its control function. BUT the system has a important secondary function - monitoring that speed signal for possible no signal. That would indicate failure of the fan and possible disastrous overheating of the CPU, so such an event triggers quick protective actions. SOME systems (apparently not your laptop) will shut down and refuse to re-start if there is NO speed signal coming from the CPU cooler fan.

The PWM (Pulse Width Modulation) signal coming from the mobo header on Pin #4 is like a square wave in that it is either fully on or fully off. For a Square Wave this signal is fully on exactly 50% of the time always. For a PWM signal that % On value is varied from 0% to 100 % and that is the information it carries. Inside the 4-pin fan there is a small chip that uses this signal to modify the flow of current from the +12 VDC line through the motor windings, thus altering the average power to the fan and hence its speed. The automatic control system uses the reading from the CPU internal temp sensor to set and adjust the PWM signal. It monitors the fan speed for failure, and most systems (apparently not yours) can show you that speed somewhere in BIOS Setup (or via a utility tool supplied with your system that runs under Windows as an app), but it does not use that for control of fan speed.

Why do you think your fan is slower than is used to be? Is it quieter than you remember? Do you think your CPU is running hotter than before? Do you feel the air flow out of the vents is low? One thing that laptop cooling systems can develop is some partial blockage of the air flow path due to dust accumulation, and that can be hard to find and remove because the air path often is through small confined places you can't see and reach easily. If that happens you can experience low air exhaust flow out of the vents and higher CPU temperatures even though the fan is trying to run high speed. On the other hand, IF you had that problem before and have cured it by cleaning when you disassembled the system, the fan may be running slower and quieter now but still able to cool the system properly with good air flow.

 

[omarCG]

In any computer the CPU chip has its own temperature sensor (in some CPU's, more than one) built in and the mobo uses that to monitor the CPU internal temp. SOME systems also use a second CPU temp sensor built into the chip socket on the mobo. For mobo temperatures there is a separate sensor on the mobo.

A 4-pin fan has 4 wires to it:
Pin #1 - Ground
Pin #2 - fixed +12 VDC power supply
Pin #3 - Speed signal
Pin #4 - PWM signal.

The speed signal on Pin #3 is generated by the fan and sent back to the mobo on this line. It consists of pulses 5 VDC high at a rate of 2 pulses per fan revolution. The mobo header just counts those to measure fan speed. Although we talk of "speed control", what this really is, is a TEMPERATURE control system. That is, the target is TEMPERATURE (for the CPU, the temp inside that chip), and the automatic control system manipulates the signal to the fan to ensure that target is met. The system does not care what the speed is - it does not even use the speed signal for its control function. BUT the system has a important secondary function - monitoring that speed signal for possible no signal. That would indicate failure of the fan and possible disastrous overheating of the CPU, so such an event triggers quick protective actions. SOME systems (apparently not your laptop) will shut down and refuse to re-start if there is NO speed signal coming from the CPU cooler fan.

The PWM (Pulse Width Modulation) signal coming from the mobo header on Pin #4 is like a square wave in that it is either fully on or fully off. For a Square Wave this signal is fully on exactly 50% of the time always. For a PWM signal that % On value is varied from 0% to 100 % and that is the information it carries. Inside the 4-pin fan there is a small chip that uses this signal to modify the flow of current from the +12 VDC line through the motor windings, thus altering the average power to the fan and hence its speed. The automatic control system uses the reading from the CPU internal temp sensor to set and adjust the PWM signal. It monitors the fan speed for failure, and most systems (apparently not yours) can show you that speed somewhere in BIOS Setup (or via a utility tool supplied with your system that runs under Windows as an app), but it does not use that for control of fan speed.

Why do you think your fan is slower than is used to be? Is it quieter than you remember? Do you think your CPU is running hotter than before? Do you feel the air flow out of the vents is low? One thing that laptop cooling systems can develop is some partial blockage of the air flow path due to dust accumulation, and that can be hard to find and remove because the air path often is through small confined places you can't see and reach easily. If that happens you can experience low air exhaust flow out of the vents and higher CPU temperatures even though the fan is trying to run high speed. On the other hand, IF you had that problem before and have cured it by cleaning when you disassembled the system, the fan may be running slower and quieter now but still able to cool the system properly with good air flow.

Hmm so k I understand now so speed signal + tempreture signal ---> motherboard and it it reports pack to pmw to control how fast fan should spin that's right ?

Also yea it's not as powerful as I remember because I usually put my hands regularly over the air vents and it's weaker than I remember, the fans are clean and also the gpu fan is much more aggressive when loaded compared to the cpu fan. However, when loaded to 99% with no overlooking it hovers around 73 while the gpu which has way higher tdp hovers around 68. I'm not sure if those mean anything but I'm stating them just in case.

 

[omarCG]

The BIOS on the motherboard helps manage the fans and the fan's curve(the speed at which it should rotate when it hits a point on a temperature curve/graph).

You could try and see if your laptop is pending any BIOS updates. As for your point about not being able to manage the fan in your laptop, might want to give this a read.

Well I have latest bios update. I also installed speed fan hwmonitor, msi afterburner. Literally none of them reads the fans they would read all different modules except for the fans, I looked around and I haven't seen anyone who's been able to control the fan nor monitor it on this specific model.

 

[Paperdoc]

Yes, you get the control strategy right. The temps you cite seem quite reasonable to me even when heavily loaded. That means the cooling system is doing its job well and there is no apparent need for more cooling.

 

[omarCG]

Yes, you get the control strategy right. The temps you cite seem quite reasonable to me even when heavily loaded. That means the cooling system is doing its job well and there is no apparent need for more cooling.

Ok that's great, thanks man!