Being a non-K series CPU means the multiplier is locked. On older CPU's (e.g. Core 2, Nehalem etc.) you could still overclock by altering the external clock speed. For example, I ran my Core i5-750 (stock 2.66 Ghz) at 3.2 Ghz (with turbo to 3.4 or 3.6 Ghz, I can't really remember) for a good few years by just adjusting the base clock from 133 mhz to 160 mhz. No stability problems at all, and as it was relatively mild, no voltage increases required.
I believe on Sandy Bridge onwards (i.e. what you have), overclocking using the base clock is not really an option. Upping the base clock causes stability problems with just a few percent increase. So basically you need a processor with an unlocked multiplier (K series) to have any chance of overclocking successfully on these systems. They also require a compatible motherboard - on newer Intel platforms, overclocking capable chipsets have a code number beginning in a Z. For example Z77, Z87, Z97, Z110.
Edited by jonuk76, 08 December 2017 - 10:17 AM.