AMD Athlon II X4 645 3.10 GHz
 

What started out as the first quad core processor under $ 100, has evolved into a powerful and very affordable all round performer. AMD's newest addition to the Athlon II Series, the quad core Athlon II X4 645 is stepping over the 3 GHz mark, clocking at impressive 3.10 GHz.
http://www.techpowerup.com/reviews/AMD/Athlon_II_X4_645