With Sandy Bridge and Ivy Bridge, standard Core i5 and i7 processors offer enough multiplier headroom for 400MHz overclocks. K-series chips are only required to push higher. Things are different for Haswell, which removes the multiplier allowance for standard CPUs, making multiplier-based overclocking exclusive to K-series processors."
Slow computer got you down? Maybe a hardware upgrade should be in your cards, if so this guide to the Fundamentals of Upgrading a PC is an invaluable read. PCSTATS Tips