BIOS freezes after CPU replacement (Windows loads and works properly). What is the reason?

Question

BIOS

I replaced the Pentium 4 processor in an old computer with a Core 2 Duo.
The system works, everything seems to be as it should.
But when you try to exit the BIOS, the BIOS itself freezes, even the clock does not run, it does not respond to the keyboard.
What can be wrong?
Reset bios to default, no help.