How to make Windows 8.1 Pro make use of all 6 cores of my CPU ?

[MarkCara]

My CPU is Core i7-5820K, it has 6 cores and I've realized that Windows 8.1 Pro doesn't use all of those 6 cores at once. I only see my programs run faster when I overclock it from 3.3 GHz to 4.5 GHz so the Windows probably just uses 1-2 cores in practice. So I wonder if there is any tweak to make the Windows make use of all the 6 cores ?

Edit : Topic was moved to here : https://bitcointalk.org/index.php?topic=1089144