Yeah, you beat me to this. No one will probably read this, but... If Superfreakonomics is even remotely objective on this topic, then it seems like IV is an engineer's dream. You get to build cool things and find solutions to big problems (reducing hurricane strength, climate change, yadda yadda), and they make money through patent licensing. But that's feeling I came away with after reading the book, and I'm giving the authors the benefit of the doubt.

At least with the general purpose registers, AMD wanted to go to 32, but couldn't do it without changing the instruction set. I'd assume the same thing applies to the SSE registers.

How so? Unless I'm missing something here, I think the only cost is in the size of the register file and rename register set, but nothing ISA-related.