Mutlipliers are almost always locked now adays.
Some AMD's can be unlocked by modifying the bridges but its risky business, Intel has always been anti-overclocker and has made it nearly impossible to unlock their multis without distroying the cpu.
Basically if your overclocking anymore its competely done by adjusting the FSB, maybe older motherboards from years ago could unlock multis when the locks where much simplier but you will find nothing like that beyond socket A.
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