> Yea it's not possible (in a way that works without breaking stuff) to drop from 64bit to 16bit the way you can with 32 to 16.
Yes, it is. It’s almost exactly the same. What you can’t do is run v8086 code on a 64-bit kernel without using a VM, most of the code people care about is 16-bit protected mode code.
I maintain the messy but small amount of Linux kernel code that makes this work. It is, indeed, gross, because the x86 architecture is awful. But it works fine in practice and there is quite a good test suite these days to exercise the ugly bits in the kernel tree.
Yes, it is. It’s almost exactly the same. What you can’t do is run v8086 code on a 64-bit kernel without using a VM, most of the code people care about is 16-bit protected mode code.
I maintain the messy but small amount of Linux kernel code that makes this work. It is, indeed, gross, because the x86 architecture is awful. But it works fine in practice and there is quite a good test suite these days to exercise the ugly bits in the kernel tree.