Right, I have figured out this long standing Zoom problem of cutting the Laptop out. It's increased recently to every day, which is a real nuisance.

The thing cuts out on temperature, but the issue is/was that the fan was only in 2nd gear (of 4) so it wasn't seriously cooling it.

That particular bit of the system is handled entirely by the BIOS. So I am left looking for

• A problem in BIOS retention in memory, which I deem to be most unlikely.
• An electronic problem in the laptop circuitry, which I am not chasing.

If it was a cpu cooling (e.g. heatsink fins clogged with junk) then the fan would speed up, right? But the fan stays slow.

Can anyone think of other possible causes? It's time to part company otherwise, because the laptop isn't worth it.

Have you installed lm_sensors and checked the actual reported temps?
If the fan is not speeding up it could be the fan profile is improperly set in bios.
It also could be that there is bad thermal paste between the cpu and the heat sink so the cpu is suddenly overheating even before the fan has time to respond.
Same thing could be related to air flow blockage. Inadequate cooling can cause sudden temp jumps in the cpu triggering a shutdown even before the system can respond and change fan speed..

I have problems with an HP laptop, especially in Summer heat, what I do is put a length of wood under it at the back, to raise the bottom off whatever I'm using it on, which allows more air circulation to the bottom of the laptop - usually works OK.

I had a previous laptop that I used to place a small fan almost against the fan outlet port to help cool it.

Neither is ideal, but they worked.

If the fan would spin faster, I'd be fine. But default action on overheat is hibernate, and this dies, like you pulled the plug.

I was wondering if the governor could be involved, which appears to be ondemand I don't know if that affects cooling.

The governor you noted changes cpu freq dependent upon load. More load, cpu freq rises to respond quicker. It is not temp related but rather load related.

You did not say what laptop you have nor the bios.
In my desktop machine I have settings in bios for the fan speed vs temp curves. The settings range from low speed and slow response to 100% speed 100% of the time, and even have custom settings available. My laptop does not have the fan speed profile.

I have found some things that help with temp of the laptop.
The air intake is on the bottom so it is critical that it has space to breath under the case. At home I always set it on my desk with one edge supported so there is more room for air flow. I also have a laptop cooler that is basically a small platform that supports the laptop with USB powered fans to blow air up onto the bottom of the case. I use that cooler when I am traveling to make certain there is adequate space for the laptop to breathe.

I would guess that the delay in fan speed increasing may be related to how fast the cpu temp rises. In mine it seems the fan speed is directly related to cpu temp. As the temp rises the fan speeds up. It also could be that the fan itself is failing and can only run at a lower speed.

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It could be the fans are set to a quite mode that is preventing them from speeding up. This is either set in the bios and/or the system settings.

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Agreed. And ditto @ computersavvy on that governor not being directly cooling related.

Have you tried installing something that lets you adjust fan speed in software (https://wiki.archlinux.org/title/Fan_speed_control) and just running the fan up to 100% and seeing if that solves the problem?

I'd also check in the BIOS if it has a 'Fan Profile' option and change it from 'Quiet' or 'Balanced' to something like 'Fast' or 'Always On' (at least for testing).

Thanks guys. Points on the Governors noted.
The laptop is a 2013 Samsung NP350C, versions of which they make still. Critical CPU temperature is 90º. The fan speeds (Set in BIOS DSDT) are

• ≤40ºC - off
• 40-60ºC - low
• 60-70ºC - higher
• 70-80ºC - Faster still
• ≥80ºC - full speed

Now if I drop to runlevel 3 and try building a kernel, the fans speed up as temperatures rise. If I build a kernel in X, the fans speed up as temperatures do. But when I'm in Zoom, the fans never go above 'higher' although the CPU heats up, overheats and the power cuts. I have it set to hibernate on overtemp, but the BIOS may override that. Zoom is significantly harder on GPU, and has a lot of QT5 stuff, but it's an APU and there's only the one temp sensor. Generally, the fans can hold temperatures in the low 80ºs as I don't have enough GPU to overcook it. But with the fan on a go-slow, it's cooking out which is not a good stress for the CPU to undergo, not to mind dumping me out of my zoom meetings.

And I haven't a clue what's causing it.

Sounds like the intermittent nature of zoom loads might be the problem. If it is mostly lower power with momentary surges then the temps might swing more wildly than the sensors are capable of responding to. Even gkrellm that is supposed to be pseudo-real-time has ~2 second lag between display updates. That is enough to allow the cpu to shutdown with wild load & temperature swings without allowing the cooling system time to respond.

I cannot suggest how to resolve it, but only conjecture on the cause. I have seen similar on my laptop a couple times, though not with zoom.

I don't agree. The fans don't speed up on Zoom, so the thing works through nearly 20ºC of heating with no fan speed increase, which would restrain the heating. That takes minutes.

Picked up a usb driven laptop cooler pad for free here.

Used to use it in my lap.
I would get off it < the laptop > quickly. It was heavy duty and a bit uncomfy.

Has 2 big 5 inch fans. Just a thought is all.

Thanks, but I haven't room for it without reorganizing basically the whole room.

I'll buy a pc if I don't find a way around this. This laptop is well past it's sell-by, and I can sell/gift it on. The cpu and Gpu are poor, which doesn't matter with simple jobs, but matters to me.

I've no use for a laptop any more - I can't even carry the thing.

What I'm wondering here is: the GPU is part of the CPU (its an APU/SoC right?) but the fans are only responding to the CPU temperature sensor? That may be the ticket - if the GPU is creating 'a lot' of heat, it will make the whole SoC warm up, but the fans never 'see' this load condition until its too late. Any way to override that with software control (see my link above) and run the fans up to a higher RPM manually and test again?

Otherwise I'd probably say get a "new" PC, as wasteful as that may seem - I've run Zoom in a Lubuntu VM on top of Ubuntu on an old AMD A10 and it ran fine once I got audio/NAT sorted out, so if this is struggling that hard 'on metal' it very likely is 'done' as far as keeping up with modern workloads.

EDIT
Something else I thought of: are you trying to use Zoom 'in browser' or in their 'app' - the performance demands of the 'in browser' variant are massive (IOW they really punish you for not installing their garbage).

The CPU is an i3-3110m, with HD4000 GPU. There is one temperature sensor, and it can't be everywhere, you're right. To judge by the values set, it's some layers away from the silicon. So, to answer your question: I have no clue WHERE anything is inside the chip package. I was a freelance 'Electronic Genius' in Industrial Electronics, and it was necessary to crystallize exactly what was going wrong with minimal information.

Diagnosis: If the single heat sensor goes up to 90ºC it cuts my box out. The fan is controlled off this same heat sensor, and increases in speed audibly, keeping the heat in check. But for some reason the fan doesn't speed up like it should when I am using zoom, and the box cuts out with the fan on low speed.

Fan settings AFAIK are in the BIOS DSDT, and not adjustable. Well, maybe the DSDT is, but it's not faulty, because when I build a kernel, the fan speeds increase.

See my link to the Arch Wiki - there are methods to control fans within linux (e.g. software control) just as Windows does. It may or may not be 'sane' on your system but it is worth looking into via lm-sensors and such, as it could be an easy fix by just running the fan up either manually before running Zoom/other GPU intensive things, or defining a more aggressive fan curve based on CPU temperatures.