The Athlon II X2 & Phenom II X2: 45nm Dual-Core from AMD

Overclocking

Both the Athlon II X2 and the Phenom II X2 managed to overclock to about the same levels. Without any additional core voltage they were able to run at 3.5 - 3.6GHz, with the Athlon II being able to go a bit higher thanks to being free of any L3 cache. With less than 10% additional core voltage I was able to get both chips up to 3.7GHz. The Athlon II X2 250, when overvolted, managed to reliably hit 3.75GHz.

Gary's sample was able to work solid at 4.0GHz while mine would fail at 3.8GHz or above.

The Pentium E6300 topped out just under 3.6GHz with ~10% additional voltage. I noticed a strange trend when overclocking the E6300. I set the FSB to 340MHz, which when multiplied with the CPU's 10.5x multiplier should yield 3.57GHz. Yet with no additional voltage, the CPU would hardly ever go above a 10.0x multiplier once in Windows - resulting in a 3.40GHz clock speed:

The chip wasn't throttling due to heat, it simply would not run at 3.57GHz without any additional voltage. As soon as I gave it more voltage or as soon as I disabled EIST, the CPU ran at its correct frequency:

All I did was disable EIST, although increasing the VID also resulted in the same thing

Even with additional voltage however I wasn't able to get the E6300 stable at above 3.57GHz.

The Pentium E6300 is actually quite competitive when overclocked and appears to scale very well with additional clock speed. It also helps that AMD's clock speed advantage shrinks once we overclock these chips a bit.