IIRC CPUs that old didn't have any internal measuring ability like modern CPUs do, later motherboards had a diode under the CPU socket that could take measurements but that wouldn't apply to something as old as a Pentium.

Id say grab a cheap laser temp gun and use that on the cpu to get measurements.

There were also flat external temperature monitoring sensors with a panel that went between the radiator or its ribs like this one: https://eab.abime.net/showthread.php?t=76928

Ydee wrote on 2022-10-18, 08:57:

There were also flat external temperature monitoring sensors with a panel that went between the radiator or its ribs like this one: https://eab.abime.net/showthread.php?t=76928

thatd be cool ... but even cooler to use a gauge out of an old car.. keep it period 🤣

I went though a phase of been paranoid about hardware temps so fitted fan controllers, good way to fill up a drive bay if missing the blanking plates as well.

But yeh most motherboards didn't have the capability, some came with a header for a temp sensor, My P2B-DS for example uses the exact same 2 pin type that come with fan controllers that you can attach to whatever you want.
Even if you don't have the sensor attached BIOS should at least mention something about temperatures even if grayed out.

My suggestion is basically to go overkill on cooling and call it a day .

a) Use a reputable socket 370 capable CPU cooler/fan (if it can handle
b) Use thermal compound
c) Add an exhaust fan inside the case to favor air circulation/renewal and reduce hot spots
d) Regularly remove dust

Optionally, get a contactless thermometer to spot check for hot spots .

kennyPENTIUMpowers wrote on 2022-10-18, 05:34:

Is there a way to measure the temperature internally, ie without using a probe (like a DMM style)..

Do you mean as in being able to measure the temperature with a case closed up, so a small probe that could be taped to the CPU with a thin cable going outside the case would be ok? Or no probe at all, so infrared sensing? I know some motherboards had a header for a thermocouple, which could then be taped to the side of the heatsink, but I don't think that was common before Athlon/P2 days. I think the P3 was the first to have an on-chip sensor, maybe?

If you just need a small probe and thin cable then some multimeters have a temperature mode that can be hooked up to a type K thermocouple.