And that's exactly what they are- very tweaked P6es. It isn't unusual to tweak an arch over a number of years if it works well. AMD kept tweaking the original K7 design all the way through Llano. K8 is to K7 as Nehalem is to Core, and Stars (K10) is to K8 as Sandy Bridge is to Nehalem. The only new CPU architectures from Intel and AMD since 2000 are NetBurst, Itanium, Bonnell (Atom), Bobcat, and Bulldozer. NetBurst was a bust. Itanium was a bust. Atom is pretty close to a bust. Bobcat is a decent low-power microarchitecture but it's not a high-performance design by any means. Bulldozer had a bunch of teething pains it appears to somewhat be getting over with Piledriver and likely will do well with Steamroller, but it wasn't clearly better than Stars at first.