It's possible but what can I actually do?
I would figure if my dell is at least build in 2008 or even 2003 and FreeBSD did install and ran, the problem would mainly be in the BIOS.
*The first thing I would do is reset the BIOS to factory default, then set time, etc.
*Then under Power Management Setup (or whatever it was called back then) I would set AC Back Function to [Full-ON]
*I would turn off-the Default Factory Boot Menu founded elsewhere so that I can see the boot terminal activity.
*Then I would find the Virtualization options and turn it on if I plan to run any VM programs.
*I would also turn-off APIC support in the BIOS. If that don’t work don’t forget to turn it back on so to continue your experiment.
this might be the only thing you have to do. I can't remember but that will cause ACPI shutdown of VM not to work. FreeBSD vBox don't need it. It could have been what setting you make for the HDD, meaning use plain HDD and not whatever sata setting.
There is nothing wrong with raw FreeBSD 11.1 RELEASE that I experienced other then an occasional freeze at startup at ACPI stuff. I blame that on my over-worked 2010 hardware. I reboot again and it's AOK.
Other then that I have seen a reboot more-then-once for no reason at all. It was due to a SVN upgrade weeks ago. A member here tested SVN and told to retry. I re-upgraded a few days latter (it had new revision number) and it solved that problem. Evidently, the developers at SVN had caught it just in time.
This could be in a p4 p8 upgrade or whatever in your case so the next thing I would do is to run freebsd-update again or go straight to FreeBSD-11.2 BETA2 right now or wait for RC2 in a few days!
And if that don’t work I install it on another machine. I may only prove that your Dell PC is too old and can only handle FreeBSD-10x or previous.
Learning ACPI would be a great thing. There is plenty of info about ACPI. I almost got into it in the past however one of these thing got me up and running again. I had gotten confuse with APIC vs ACPI when I left off. Whatever the case its might not be a big deal. Pay attention to figure out what actually fixed it and let us know, it's still so major.
From that point I heard about flash-BIOS but finding and working with firmware (if that's what it's call) is a trip i think. Computing and expecially FreeBSD has too much going on to learn about everthing. ACPI is a trip that might change in a FLASH. FreeBSD has all I want learn. That is all that I can figure. You have just have to play hard until you find it.
Good Luck!
PS:
One more thing. Unplug the system. Check to make sure that your CPU and memory sticks are seated properly (and every thing else). Remove them all anyway and carefully reseat them. I would remove the CPU, clean it and give it a fresh coat of thermo grease. Then I would remove the computer battery for at least an hour. 24 hours recommended. Blow out your Power-Suppy. Now that I think about it I had one running but it was weak, I change it and the booting problem (or whatever was wrong) was gone. I bet that is your problem. You can't tell anymore -- the fan is spinning anyway. That was a new one on me and it was only last week when I change it. I been having hardware problems placed on the backburner for over a month now. Whatever all those problem was it's now gone off of one of my three 2010 machines (my main one)! I bet thats it!
And if that don’t work just get another
old computer - - 2010 or newer (50 - 100 bucks).