Why is there Core temperature difference?

[Matrix]

I'm running a Asus P5Q-E with a Q9550 (Arctic Cooling Freezer 7 Pro)i have clocked to 3GHz but when i run OCCT the temps go to :-

CPU1 - 77
CPU2 - 77
CPU3 - 70
CPU4 - 71

And it's the same when the system is on idle


CPU1 - 43
CPU2 - 43
CPU3 - 37
CPU4 - 44


Would it have anything to do with the paste i just put on (Arctic Silver 5 Thermal Compound )



Any info would be great please.


Thanks.

 

[Matrix]

Using core temp and tjunction is set to 0