Issue with multi core CPU on new install

Well, I tried again this morning, leaving all 4 cores enabled in BIOS.
It froze as before before even showing the installation script.

But I let it run.

1h later; blank screen, no keyboard response

I let it run

1h later (so 2h total): install script was displayed and I could start it.

It did detect the 4 cores.
It is now installing (albeit slowly, and still hasn't detected the EMMc)
we'll see how it goes

2h later the install is complete (where it used to take a few minutes from the same media/drive)

Booting seems to start and switches to blank screen, but I guess I'll be patient again and see how it goes
I think I saw some lines of text and "probing EDD" before screen went blank, but it went too fast to be sure

2h later; still blank screen, no text, no cursor

many hours later; no change

Did a hard reboot and will let it be until tomorrow

12h later, no change, still black screen

I don't know when, but 30mn later it was up.
logged in, restored backup, then ssh and lscpu shows the 4 cores.

Restarted, and 40mn later, it still isn't up.

So if boot time is >12h, that's going to be a problem.....

so I've been searching about that "probing edd" message being the last one displayed.
I found several topics, and I tried to edit grub at boot to test

adding acpi=off at the end of the 2nd line fixes it.

But then the system clock gets bad...
same as community.sophos.com/.../zbox-327-nano---sophos-utm-9-5-wrong-cpu-cores

https://askubuntu.com/questions/139157/booting-ubuntu-with-acpi-off-grub-parameter

Try pci=noacpi instead?

Because I'm persistent, I'm trying :D
Following this; https://wiki.ubuntu.com/DebuggingACPI

acpi=off => Fast boot, bad clock (too fast)
acpi=ht => hangs
pci=noacpi => hangs
acpi=noirq => hangs
pnpacpi=off => hangs
nolapic => boots faster, then hangs at splash screen