Bafore the Athlons, AMD named their IA-32 line Kn where n was some integer. So preceding the Athlon were the K5 and K6. The Athlon was going to be called the K7, but somone in marketing decided that if Intel was using bizzare names like "Pentium" rather than meaningful numbers, then AMD should do the same. And so K7 became the Athlon. The XP and MP were also K7s, just better ones. The Athlon64 and Opteron are basicly the K8. There is a lot more to them than just the AMD64 instructions. In fact you should ignore the extended mode as it will do absolutely nothing for a normal user but caus