So what are the specific setting I need to change to make it 4.2ghz, and also if I can make this i7 930 4.2ghz why didnt intel do it? Surely they know with a better fan or water cooler this can be done. Its not exactly a trade secret.
Nobody knows why Intel chooses the exact cpu speed that they do. There are lots of factors involved, and lots of reasons for Intel to be very conservative with their speeds. If they rated the chips a much faster speeds, more of them would be burned out due to conditions beyond Intel's control and people would be unhappy. This is the beauty of their new turbo mode- it senses when it is OK to overclock the processor and does it.
1. For sure they use a small and inexpensive cpu cooler, which will limit overclocking. They could put in a bigger more expensive one, but then some people would have trouble fitting it in their cases.
2. There is some variation among chips. Some will overclock better than others.
3. There are variations in where the completed PC's operate. Some are in airconditioned buildings, some are in factories, some are in buildings that aren't air conditioned on weekends, IOW some operate in areas that might be pretty hot.
4. Not very many people take care of their computers. The computers and fans get clogged with dust, the fans die and they don't get replaced, the computers get put in places where the ventilation openings are blocked.