My laptop is running extremely hot after upgrading to fedora 25. Core Temperatures reach 96 degrees. Nvidia Optimus is disabled and Onboard Intel Graphics Only mode set in BIOS. Not sure how to diagnose or fix the issue. Fedora 24 used to run cool without issues which leads me to believe its a software issue. HW and SW details are as follows;

Laptop: Lenovo T420s
Processor: Intel i5-2520M
Graphics: Nvidia GPU NVS 4200M (Discrete) & Intel HD (Onboard)
RAM: 2x 8GB

OS: Fedora release 25 (Twenty Five)
Kernel: 4.13.5-100.fc25.x86_64

Happy to provide more details ..

I don't have Optimus hardware, but temperature problems like this are serious, so I understand the need to get it sorted quickly. You mentioned that Optimus is disabled in the BIOS, but I assume you have bumblebee installed?.... and it would be good to confirm this via the OS perspective. I still wonder if the nvidia chipset is really powered down? Can you hear fans running? (I suspect not.)

Here's an Optimus page (for Antergos), but it covers some good diagnostic steps regarding an overheating laptop. Refer to the 'Missing power off' section.
https://antergos.com/wiki/hardware/b...vidia-optimus/

It mentions testing by running these commands, and checking that the discrete card is reported as 'Discrete video card is off.'
Hopefully, after the last command the nvidia card is still off.

Just in case the following are helpful regarding ThinkPad fan control....
https://wiki.archlinux.org/index.php...Pad_T420s#Fans
https://gist.github.com/abn/de81ba41...db3ee4aa83e035

You need to check the CPU speed as well. Thinkpads have a nasty habit of running the CPU at 100% all the time, whatever the load, and this tends to overheat them. The power CPU setting should be set to ON DEMAND with a minimum of about 7% and you may need to find the correct power drivers for your PC/OS .

I'd boot with the acpi=off parameter until you get it solved. OR, the cooler might be plugged with dust.

Thanks to all who replied. As I have a big project to work on I could not spend more time to diagnose the issue. Therefore, I had to bite the bullet and took the laziest way out and wiped my system and switched to ubuntu (on the assumption of better HW support) - and now the system is running typically at 47 degrees..with peaks at 67 degrees. I'm sure it was a small problem to fix - for the user with the requisite linux skills. I'm worse off from admin point of view, as I'm even less familiar with apt tools but this will get me going. I cloned my original system, so I can sort it out when I have some free time.

THANKS to all.

I'll mark this thread as closed.

Thanks for the update. Sometimes one has to be pragmatic about these things. Life is too short.