Overclocking phenom x2 550 black edition

Revision c-3 Chip

So mine unlocks to a tri core. Core 3 seems to be bad and is now disabled. What I've noticed is it takes less Vcore to stablize this chip unlocked to 3 cores at 3.8ghz (1.36 volts) than it does to stabilize 2 cores (1.4- 1.425 volts) at the same speed when it's a locked X2. To reach 4ghz on the tri configuation I just need to bump up the voltage a touch, but as a X2 I need to set it upwards towards 1.5 volts..

Can anyone explain how in the heck is that possible?

Does COH use more than 2 cores if available?