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Keep in mind that if you drop the old stuff, you'll have to provide a bootloader and even then it'll be weird; modern systems still boot in 16 bits, bootstrap in 32 bit mode, then configure 64 bit. Unless UEFI fixed that madness?


The processor itself still boots up in 16-bit mode. UEFI does switch into 64-bit mode before booting an OS loader, but that doesn't mean the processor itself starts in 64-bit mode.


UEFI starts you off in protected mode or long mode with identity paging. It even lets you package up your loader as a PE file.


UEFI can drop you directly in 64bit mode.

The problem is it uses a different memory map than 32bit mode so a lot of write your own os manuals are just flat wrong.


BIOS itself can be implemented as 32-bit code, which contains software emulator of 16-bit code. This emulator runs until CPU is switched to 32-bit protected mode by OS bootloader.


Yes it did.


If by "modern" you mean "EFI" you are incorrect.

A traditional BIOS is hardly suitable for describing a "modern" firmware; for chrissake it doesn't even use 32 bits!




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