One other general comment....
with apple dropping the Power PC chips and with the AMD parts beeing almost 100% the same as an intel part (at least so far as running programs on them anyway) I wonder amout the way that tends to give us a kind of "hardware monoculture"
in plant sci. a monoculture is generaly seen as bad due to pests and such, 1,000,000 acers of the same kind of wheat can be wiped out really fast but if you had 3 kinds of wheat + 2-3 other crops ...
even the iPhone and the ce devices ARM chips are used in them...
just another side to the story...
Well the reason x86 is so popular is mostly because of Windows. Windows (desktop) only runs on x86 - not because it's impossible to port WINDOWS itself to any other arch (it's been done before, even in recent times). It's impossible to port all the software
that runs on Windows which explicitly is compiled to x86. Because not one organization controls it all and there can be software out there in use without the source code left or the company who made it is bankrupt, and still this software is important.
So porting off x86 is hard/impossible. That's the only reason we still even use the arch. Really it's a terrible arch (4 GP registers, wtf?). In fact, x86 is so complex, so braindead of a design, that there doesn't even exist an REAL x86 processor today.
No one would dare dream to make one. Internally AMD and Intel processors have a different instruction set and different arch, they just expose an x86 instruction to the outside. There is this level on indirection (like a virtual machine IN the hardware) built
in for compatibility and it costs a substantial amount of circuity to implement (this "microcode").
ARM is much better - it can be implemented efficiently WITHOUT microcode, the instructions are executed directly by the processor, so it gets better per transistor performance that x86 can ever dream of. (The reason ARM processors are slower then modern
x86 is because they use FAR less transistors, it has nothing to do with the arch itself). It's instruction set is very consistent, easy to understand.
MIPS is also a lot better. One of the purest and simpiest instruction sets around. Both are very simple cores (RISC) but manage to pack in a lot of useful instructions and many more registers then x86.