By the way, today I have received a new Q95xx CPU (LGA 775). Tested it at a computer service by running memtest to avoid killing my motherboard by shipping an intentionally bad CPU to me (who knows).

So I have changed the CPU today from Celeron D to Q95xx (going to me_clean and libreboot it later) and very strange things begin to happen:

After installing new Q95xx CPU into GA G41M motherboard undesirable reboots begin to happen especially when I try to select something by keyboard.

I tried to download me_cleaner and reboots begun to happen more often during I was reading the docs. I have disconnected Ethernet Internet, but reboots continue.
Sometimes they rebooted in a cycle without ability even to reach GRUB4DOS, then I powered off for a few minutes and turned on again.
I have reflashed BIOS using Gigabyte recovery but reboots continued but a few more seldom.
General everyday workstation Devuan kernel stopped to boot at very beginning somewhere about CLK,
tried several times and it did not boot.
But other LiveCD booted OK, I tried different versions of SystemRescueCD and Slax.
In all of them current day of week for the correct today number of day (in terms of month) in the calendar was shifted by two days, I checked on another notebook computer not related to this hardware and there day of week was correct.
After mounting ZFS from SystemRescueCD (with integrated ZFS modules) I tried to chroot and install another old 3x kernel into Devuan, but was not able to rebuild ZFS modules for it because /usr/src was missing any files for some unknown reason.
Also I discovered that /home/xxx_user is empty too. (After reboot contents of these two folder returned back, so I guess it was somehow hacked at VFS level to make me think they are blank).
Then I rebooted and tried to boot Devuan again and it booted without stopping at CLK.
I tried to poweroff for a few minutes to reset CPU microcode, but if it was a microcode issue may Intel CPU have a flashrom inside them for microcode? Devuan booted OK again without hanging on CLK step, so repeatedly already, all these steps WITHOUT Internet cable in the system.

Other possible reasons I can expect could influence too:
    Thermal gel could get on the CPU and worsen the contacts which could make the system unstable until contacts improved under cooler presser.
    During all earlier night memtest did not find any errors, but could possibly heat the board and old capacitors, which could make the board unstable for a few hours after the stress.
Actually I have looked in the BIOS at CPU temperature and it was 23 celsium degress most likely due to a very good and big Lucifer K2 cooler.
    It is an impression, that reboots were not random, but like a coincidence of my thoughts to negative emotions agains the ganstalkers (you know, they read human thoughts?), that is why I think there is a radio chip for remote controlling something like IntelME  on even very old motherboards GA G41M ES2L and/or may be in top CPUs like Q99xx.