We kept the same 1.60 V limit already applied to our Core 2 Duo E6750 in part one of this two-part series, and thus reached this processor's same 4.16 GHz frequency limit.

Even though it contains two of the same dies on a single socket package, the Core 2 Extreme QX6850 was not nearly as FSB-friendly as the E6750. Even at its standard 9x multiplier, the QX6850 barely exceeded 3.80 GHz, so we tried a 10x multiplier and finally breached 4 gigahertz.