Apparently it only works on certain Biostar boards. So it's more likely a bug in some BIOS than an actual, intentional capability of the chips themselves.
Besides, given that X3s are X4s that were tested, found to have a core that malfunctioned, and had the bad core disabled rather than throwing the whole chip out, it's a good bet that even if you can unlock the core, it's not a good idea to do so.
- Diosjenin -
well that post sucked