As far as the Athlon II and Phenom II, they use the same core/s. The difference is how much L2 and L3 cache they have. The Athlon IIs that have 512 of L2 are decapitated Phenom II and the Athlon II that have 1mb. of L2 are true dual cores but still have the same core design.
Thats Regor only (dual cores), the Athlon II X3 and X4's have 512mb also.