Re: Going from 32 to 64 bit was so simple nobody really noticed it happened
> apparently in 64-bit mode (which they call "long" mode) you can have 16-bit protected mode processes
16-bit protected mode is 80286 native mode. The 80286 was brain dead so nobody cares.
> Because, in theory, a "well behaved" 16-bit application SHOULD be possible to run in 64-bit mode...
It may be that "in theory" a particular design could run 16bit V86 and 64bit together, but the AMD design does not. Programs run by executing instructions. Instructions have particular bit layouts. These have a number of bits assigned to the op-code. You cannot have more different op-codes than the number of bits allow. AMD-64 long mode requires additional op-codes so they reused some numbers that overlapped stuff that was 20 years out of date.
Virtual86 and Real86 are for running 8086 programs, that design is from 1978 - 40 years ago.
Biting the hand that feeds IT
