I did that with a Phenom II X2 555. The 3rd core was stable up to around 3.8ghz if I remember correctly, whereas the 2 enabled by default were fine up to at lea

I did that with a Phenom II X2 555. The 3rd core was stable up to around 3.8ghz if I remember correctly, whereas the 2 enabled by default were fine up to at least 4.2.