Yesterday it was unveiled that some Phenom II X3 processors can easily be unlocked to get access to all four cores, and today VR Zone received confirmation from motherboard makers that this is indeed possible. To make this trick work, you'll need a Phenom II X3 from the 0904 batch and a motherboard with ACC support. You'll also need to test whether the fourth core is stable enough, because the triple core series was originally created to get rid of defective quad-cores so there's no guarantee that this unlocking will work.
To verify those claims, board makers too had done some internal testings and so far achieve some success as well. Above is test done on the DFI 790FX board and similar success stories are reported from the labs from Biostar, Gigabyte and others as well.
From what we know, only 0904 batches of Phenom II X3 can be unlocked. Basically, it just uses ACC core to trick the CPU to enable 4th core that has been classed unstable by AMD. However, not all unlocked Phenom II X3 will be stable so you will need some luck here.