It's definitly hard to say for sure as others have said, but I can share a similar experience.

Any Proliant server I have worked with always manages to power on with a CPU, supported or not. If it is an unsupported CPU due to unsupported firmware, it sits at a very basic "CPU UNSUPPORTED" message and starts looking at the floppy drive for a firmware file. It has enough logic to get it updated to then support the CPU. This comes in handy in situations where not all the spare mainboards have been upgraded, and a customer has one replaced.

I can't say for sure though if this tech has moved into common desktop motherboards though. It's beein in Proliants since at least 1998, so I would hope so. Then again, it's still rare to even see a PC motherboard with the ability to have the BIOS upgraded in Windows, or Linux.