I wonder if one forcefully disables all ACPI support and drivers, are they allowed to go back to the binary ON/OFF lifestyle on a modern x86 system? What does Windows do?
I think so - but it would be fun to confirm. Windows up to and including XP still have the AT shutdown splash baked in. I think the splash was dropped with Vista. I did successfully boot Vista on a real AT-style motherboard but I don't recall how the shutdown looked.
One can install Windows 98 without ACPI by running setup with the "/pi" switch, alternative one can uninstall the "ACPI PC" device and replace it with "Standard PC" which should disable ACPI. This should cause it to show the shutdown splash even on ATX systems.
