Replies to post #26605 on Advanced Micro Devices Inc (AMD)

[j3pflynn]

fpg - re: microcode
is Intel's technique - maybe
will be Intel's technique for any lengthy period - unlikely

[wbmw]

fpg, Re: At the fundamental technical side of things, IA32E is an instruction extension - a microcode edit.

>> As an AMD investor, I sure hope this is Intel's technique for adding AMD64 compatibility.

Maybe I'm explaining this wrong.

64-bits in general is up to the microcode implementation. AMD designed a 64-bit ALU, and they wrote the microcode to create the set of instructions that made up AMD64. Modern ALUs can do all the adds, multiplies, shifts, etc that make up the instruction set - it's only a matter of defining the op-codes that will execute them. All of this is defined in the microcode.

Intel did the same thing. They created a general purpose 64-bit ALU which might or might not have had microcode compatibility with AMD. In order to make it compatible, you don't have to change the pipeline, or build a new ALU. It still works the same way, because modern ALUs are general purpose. I think Intel wrote the microcode to be compatible with AMD64 when they realized that Microsoft was not going to support two separate x86 instruction sets.

If you think that it takes a complete redesign of the core, then you would be mistaken.