[Bug 271938] Excessive heating on Lenovo Thinkpad E450 even with CPU @ 100% idle

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=271938

            Bug ID: 271938
           Summary: Excessive heating on Lenovo Thinkpad E450 even with
                    CPU @ 100% idle
           Product: Base System
           Version: 13.2-RELEASE
          Hardware: amd64
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: kern
          Assignee: bugs@FreeBSD.org
          Reporter: chenpan@protonmail.com

Created attachment 242716
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=242716&action=edit
dmesg info

Machine & Model   : Lenovo ThinkPad E450 (20DDA02WIG)
CPU               : Intel Core i5-4300U
GPU               : Intel Haswell-ULT Integrated Graphics
                  : AMD Topaz XT [Radeon R7 M260/M265...]
Year of Purchase  : 2016

Issue:
My laptop generates excessive heat even without any CPU usage (~100% idle),
even when the clock speeds stepped all the way down. The issue seems to be OS
(FreeBSD) dependent.

Context: 
I am moving from Linux to FreeBSD, and when I first booted the FreeBSD
13.2-RELEASE DVD, I sensed a lot of unusual heat emanating. The heat persists
even after installation and it heats up again as soon as the installed system
is rebooted from a complete state of cool down and rest. This happens with both
when using the live DVD and after a freshly installed system, tested on both
13.2-RELEASE and 12.4-RELEASE.

Observations:
- This issue seems to be OS-dependent and it is noticeably cooler in Linux. I
confirmed this by reinstalling Linux to verify and installing
freebsd-13.2-RELEASE again.
- It's not just the different reported temperature, I can actually feel the
heat, that's when I first noticed and decided to test further. 
- Changing dev.acpi_ibm.0.fan: 1 -> 0 and dev.acpi_ibm.0.fan_level: 0 -> 7
settings did not do any good.
- Powerd is enabled and running and seems it has no influence.
- The issue persists both with and without acpi_ibm loaded.
- The temperatures in Linux varies from 43-48 C, while FreeBSD temperature
ranges from 53 to 59. This is mostly with CPU @~100% idle.

File Attached:
- dmesg.boot (dmesg_boot.txt)
- output of sysctl dev.cpu (sysctl_devcpu.txt)
- output of sysctl hw.apci (sysctl_hwacpi.txt)
- output of sysctl dev.acpi__ibm (sysctl_devacpi_ibm.txt)
- rc.conf (rc_conf.txt)
- loader.conf (loader_conf.txt)

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