AMD Athlon X4 860K OC Issue

Hello, I overclocked my CPU for the first time but I have an issue, two of my cores are at 4 GHz while 2 are at 1.7 GHz. Why is this? http://imgur.com/rWcWD19

Oh yeah, should I use motherboard BIOS or AMD Overdrive to OC? I have a Gigabyte GA-F2A78M-D3H motherboard.

Thanks!