Hi dude,
the standard clock multiplier for i5 6600 (Non-K) is 33 - higher multipliers are only applied via turbo which is is not used in Skylake Non-K OC Bioses.
So the calculation you want to do is 4400 divided by 33 = 133.34 BCLK. Means set your BCLK to 133.34 and your on the desired 4400 Mhz.
Happy oc`ing. Greetz.