With design of new K10 microarchitecture, by majority of critics, AMD bit off more than they can chew. In beginning K10 wasn't designed for two or single core CPUs. For less cores it was necessary to take "rejected" CPUs and disable faulty cores, and that isn't a cheap process. CPU with disabled core still has same surface area as quad core, and disabled part is totally useless. This can be profitable if yield is relatively low which will result in large quantities of "defected" CPUs. One of the reasons why we waited so long for KUMA core is low yield of Phenom CPUs which resulted in low amount of rejected CPUs that can be converted to Phenom X2.