GPU option ROMs no longer make assumptions about legacy setup - UEFI option ROMs are executed in either 32-bit or 64-bit mode, and there's no need to implement

GPU option ROMs no longer make assumptions about legacy setup - UEFI option ROMs are executed in either 32-bit or 64-bit mode, and there's no need to implement any of the legacy VGA compatibility. Same for PXE, which just hooks into the UEFI network stack rather than having to deal with anything legacy. No OS assumes real-mode for the boot processor at this point. If you boot Linux on a UEFI system you'll jump straight into the kernel in 64-bit protected mode. The only time real mode comes into play is in the bringup of other CPUs (which is something that can be ignored now that ACPI specifies an alternative) and ACPI resume (which isn't relevant on systems that use S0ix rather than S3), so you could absolutely ship an x86 CPU that didn't support real mode and all you'd have to do is modify the firmware entry code. Modern operating systems would Just Work, as would hardware option ROMs. (And enough systems no longer ship with CSMs that people aren't using FreeDOS for firmware updates any more - it's either Linux or a UEFI executable)