Rusty_3 :
I have seen a guys cpu-z screenshot where his 4340 was running at 3.7 and he had mentioned something about BCLK/straps 100mhz
Does anyone know how to do this and is it limited by motherboard?
It is limited by the motherboard.
I wouldn;'t mess with that unless you really know what you are doing(and you don;t if you ask this).
While on SKylake BCLK OCing is ok, with Haswell it's a totally differt beast. In simple terms, on Haswell, when you increase the BCLK you're overclocking everything, not just the CPU. There are ways to ammend this, but, if you want to get into it, you're in for a steep learning curve.