Hi, I've been trying to overclock my cpu (i5 6600k skylake) to a 4ghz overclock on a gigabyte motherboard and I try typing in 40 as the multiplyer but nothing changes? And I when I hit + on the num pad it will NOT go past 3.9ghz. I don't why this is, I haven't changed the voltage as I do not wish to increase it more than the stock voltage so if anyone knows why I cannot get 4ghz overclock please let me know!