Edit: It's the model number and the Name.

Quote Originally Posted by villa1n View Post
obviously phenom is the name designated to triple and quad offerings, and amd would like to differeniate dual core offerings by keeping the athlon name alive and associated with x2 and value offerings, like they have on their mobile line.
Yet, still seems a way to confuse folks. Yes, they've lied about the old models as well.
Quote Originally Posted by PC World

The 3000+ Skinny

AMD is shipping three new Barton-based CPUs: The Athlon XP 3000+ (running at 2.167 GHz), a new XP 2800+ (2.083 GHz), and the first XP 2500+ (1.833 GHz). All three include 512KB L2 cache and a 333-MHz front side bus. The 2800+ Barton-based CPU replaces an existing Athlon XP 2800+ chip that AMD shipped in limited quantities to five PC vendors in the fall of 2002.

The original 2800+ chip runs at 2.25 GHz, which is faster than both its replacement and the 3000+ chip. What gives? "The bottom line is the 2800+ model number is derived from application performance," says AMD spokesperson Damon Muzny. The new 2800+ uses more cache instead of more megahertz to reach a specific application speed level, he adds.

All 2800+ chips shipping in PCs should be Barton-based models by the time you read this, Muzny says. (And chip pricing will be the same, so there's no bargain-hunting opportunity.)
BS because it still ran slower on most tests even with more cache. Also the same price for a slower model with more cache but slower more times than not.