[cbsmith]

> It would seem that Intel and AMD have to play a very conservative game with compatibility and building a product that increments support for x86 and x64.

Talk to people who design chips. The compatibility barely impacts the chip transistor budget these days, and since the underlying CPU isn't running x86 or x64 instructions, it really doesn't impact the CPU design. There may be some intrinsic overhead coming from limitations of the ISA itself, but even there they keep adding new instructions for specialized operations when opportunities allow.