How exactly does the fan know what speed to rotate at a certain temp? Is there a program that checks the recorded temperature output of a sensor, and then based on the recorded temp, changes the input to the fans? How exactly does the later work?
What component checks this temp and sends a voltage/pwm signal to the fan?

 

CPUs have embedded thermocouples. They are in various places and a relatively complex program on the mainboard takes the measurements of those, and possibly others attached elsewhere, to manage cooling—or in the case of thermal overlaid—shutdown the computer to prevent destroying the CPU or other components.

 

CPUs have embedded thermocouples. They are in various places and a relatively complex program on the mainboard takes the measurements of those, and possibly others attached elsewhere, to manage cooling—or in the case of thermal overlaid—shutdown the computer to prevent destroying the CPU or other components.

Thank you for the response,
I believe newer CPUs utilise IC digital temperature sensors? Correct me if I am wrong.

 

Intel started with DTS (Digital Thermal Sensors), I think, in the i7. They are not digital sensors, though, despite the name, They are analog sensors with colocated ADC (Analog-to-DIgital Converters) right on the CPU so what comes out of the CPU is the digital readout rather than a sensor voltage.

It simplifies things.