As CPUs operate they always generate heat but for every cpu the temprature at which it operates is very important, and all cpus have an upper limit beyond which they should not be allowed to heat.
Here are various ways in which we can find the temprature of the CPU core at any given time.
$ sensors acpitz-virtual-0 Adapter: Virtual device temp1: +43.0°C (crit = +90.0°C) k8temp-pci-00c3 Adapter: PCI adapter Core0 Temp: +34.0°C
The first set of the readings is the core temprature used by the ACPI. The second is of a PCI adapter.
In the first set of reading we can see that the critical temprature is mentioned as 90.0°C, operating the CPU beyond that tempratiure would harm the CPU and mACPI would always shut the system down as soon as the critical temprature is reached.
$ acpi -V Battery 0: Full, 100% Battery 0: design capacity 4400 mAh, last full capacity 3722 mAh = 84% Adapter 0: on-line Thermal 0: ok, 44.0 degrees C Thermal 0: trip point 0 switches to mode critical at temperature 90.0 degrees C Thermal 0: trip point 1 switches to mode passive at temperature 88.0 degrees C Cooling 0: Processor 0 of 3
Norte the “V” is in upper case The fourh line gives the temprature of the core and the fifth line the critical temprature.
The above command will work only if you have ACPI enabled in the system.
$ cat /proc/acpi/thermal_zone/THRM/temperature temperature: 45 C
The above proc file system will exist only if ACPI is enabled. Other than temprature we can find the critical temprature using
$ cat /proc/acpi/thermal_zone/THRM/trip_points critical (S5): 90 C passive: 88 C: tc1=2 tc2=5 tsp=50 devices=CPU0
passive trip point is one at which the hardware is cooled by lowering the cpu freuency etc. Not all hardware support this.