One of the big selling points of AMD CPUs is the ability to unlock cores on the Phenom II X2, X3 and even Sempron 140 Processors. This is possible due to the fact that AMD uses one standard Agena die for its quad, triple and dual Phenom IIs.
However the problem is the fact that AMD sometimes uses faulty inventory to fill lower rated products so on a Phenom II X2 1 of the disabled cores maybe faulty so unlocking this core would cause instabilities.
Unfortunately when unlocking cores on the Phenom II X2 you would have to unlock both cores and therefore if one of them cores was faulty the system would be unstable and you would have to revert back to the dual core option.
Asus are trying to overcome this with the release of a bios update for 17 of its AMD motherboards which will allow the user to unlock a choice of 1 or 2 cores and also which core to unlock!
Asus’ advantage is that if you have just one bad core, you can specify the BIOS to unlock a single, specific core to give you a free triple core that’s far more likely to be stable and overclockable.