You could overclock it, but that may not be an option if you have an i7-4770 rather than an i7-4770K, or if your motherboard won't let you do it. As far as I know, Turbo Boost can't be controlled. You can enable or disable it, but if enabled, it does its own thing.
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There's a way to do what you're asking with Xeon processors. Unfortunately I have no idea how to give you any sort of clue on where to start looking outside of maybe googling "Xeon turboboost hack". I also have no idea whether or not said hack will work with an i-series processor.
Out of curiosity, why are you wanting to do this? In any situation where turboboost would be beneficial it should turn on automatically and stay on until heat becomes an issue (or power on laptops, or if you have a PSU that can't keep up).
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