They added their own external clock generator which circumvents the Intel safeguarded clock generator in order to allow the modification of the BCLK (Base Clock). It provides limited overclocking support, but without the ability to modify the BCLK multiplier, results won't be spectacular. It's a step in the right direction. Kudos ASRock!
Source
- http://www.kitguru.net/components/motherboard/matthew-wilson/asrock-re-enables-overclocking-on-non-k-intel-cpus-with-new-motherboards/