Don't play dumb, you already know what I mean,
I'm not sure I understand what you mean. You seem to think AMD64 is not a full blown 64-bit architecture, but you haven't stated why. It has been shown already AMD64 has a long mode (which 64 bit Linux and Windows use), which is a full blown 64-bit mode with 64-bit virtual addressing and registers. It even has a compatibility mode the O/S can switch into for running existing 32-bit apps natively (albeit with a small translation layer for o/s and system calls made by the 32-bit application).
If you don't mind the x86 instruction set, there is no more elegant solution than this.
edit: oops - sorry Semi - I see you changed your mind in a later post. I should read all posts before replying...