Pot luck more like. If what I understand is the case is correct, getting a four core system from an X2 chip isn't guaranteed. Where Intel have different dies for the Core2 Duo and Core2 Quad chips I believe AMD use the same die for the Phenom II X2, X3 and X4, disabling the cores they don't need on the X2 and X3. For Intel, a faulty core on their quad chip means its unusable, so any defects mean the chip is headed for the skip. AMD, on the other hand, simply disable the faulty core(s) to create the X2 and X3 chips from the X4 meaning they have far less waste. When demad for the X2 and X3 outstrips the number of X4s with faulty cores, they simply take a good one and disable cores to get what they need. So, if you are lucky enough to get one of these you effectively get an X4 chip for the price of an X2 (or X3). But if you're unlucky the disabled cores are faulty and either they won't run or will be unstable. So, it is well worth trying to enable the disabled cores on he X2 and X3 if you can (getting something for nothing is always worth a try), but the only way to guarantee having four stable and fully functional cores is to buy an X4 chip in the first place.
