An Introduction to 64-bit Computing and x86-64.
When I first heard that AMD had plans to extend the x86 ISA to 64 bits, I thought it was a terrible idea. Though x86 is the world's most successful ISA, it's also the world's most widely disparaged. Programmers, analysts, architecture buffs, and enthusiasts often see x86 as a leaden albatross around the neck of the entire computing industry, and like the Mariner's albatross we were all hoping it would just fall off at some point and slip quietly into the deep. But in spite of such hopes, I really knew better. In fact, I've argued elsewhere that x86 isn't going away anytime soon, and it no longer makes any real sense to gripe about its quirks from a performance perspective. I won't recap that argument here, but I can sum it up briefly. Read more at the source