Apparently customers that own an AMD Phenom II processor can turn the
3 cores into 4 cores, or make it a quad core without any hardware
modifications. According to the source, it requires a Biostar
motherboard but some other motherboard's might have the same feature
located in the BIOS. Be warned though, usually when AMD or Intel ships
a CPU with one of the cores disabled, it's because they probably had
issues with running the extra core on that specific CPU. It could be
due to heating, performance, or some other issue.