I stumbled upon a nice article on Instruction Set Architecture (ISA) at http://www.arstechnica.com/cpu/2q00/...future-1.html. It discusses the future of x86, the history of the ISA, benefits and problems with ISA's, emulation, translation, JIT, Transmeta's Crusoe.

http://www.arstechnica.com/cpu/2q00/...-future-1.html