Advanced Micro Devices Inc (AMD)

[HailMary]

x86-64 would have been an ideal opportunity. It's been missed.

x86-64 long mode does not support many of the things you listed, save for variable length instructions. These things can't be dropped, however, until legacy 32-bit apps are no longer important. So a phase out can happen in 2 phases.

Phase 1, drop legacy modes. This can happen when everyone has moved to a 64-bit o/s, or at least at the point when AMD and Intel don't feel the need to support older 32-bit o/s-es with their newest chips. This is probably at least 5 years off.

Phase 2, drop 64-bit compatibility mode, which allows running 32-bit apps under a 64-bit o/s. That is at least 10 years off by my guess. Look how long windows had to carry around support for 16-bit apps when the move to 32-bit mode took place.

After phase 2, pure x86-64 long mode doesn't have much baggage left.