I'm rewriting an embedded BIOS for an Intel processor at work and It's been a bit of a clicking point for me about how modern X86 really works. Nothing EFI or the like, but still very instructive.
Now if only I could get DCI to work...
Now if only I could get DCI to work...
What's different about modern x86 compared to the old standards?
The “too long; didn’t watch” summary is that there’s several peripherals, timers, RTC, etc outside of the processor that software will expect to be present (or at least emulated) with specific interfaces. You can implement x86_64 without a lot of this, or redone in a more modern style, but software such as a Linux kernel will have to be patched for it.
Typically a modern laptop will have all the legacy peripherals emulated, and the modern peripherals will live alongside them.