Historically, AMD's CPU families were given a "K-number" (which originally stood for Kryptonite, an allusion to the Superman comic book character's fatal weakness) starting with their first internal x86 CPU design, the K5, to represent generational changes. AMD has not used K-nomenclature codenames in official AMD documents and press releases since the beginning of 2005, when K8 described the Athlon 64 processor family. AMD now refers to the codename K8 processors as the Family 0Fh processors. 10h and 0Fh refer to the main result of the CPUID x86 processor instruction. In hexadecimal numbering, 0F(h) (where the h represents hexadecimal numbering) equals the decimal number 15, and 10(h) equals the decimal number 16. (The "K10h" form that sometimes pops up is an improper hybrid of the "K" code and Family XXh identifier number.)
