Odd temp difference between cores

[Opty1218]

I recently downloaded and tried CoreTemp to see how my cpu temps were, but i was surprised to what I saw. There was a huge difference between the core temps, so I removed cleaned and reseated my heatsink (TR Ultima-90) with some AS5. I know AS5 has a burn in time, but I still came up with a weird reading.
Idle theres a 15C difference between core 0 and core 1. In this instance, one core is running twice as hot as the other.

And after running Prime95 for a bit I came up with this, which is still odd to me with a 12C difference between the cores.

Is this normal? or is it just some compatability issue between CoreTemp and my Opteron giving weird results?

 

[Nenu]

My A64 x2 was similar.
Either they arent being read properly or one core has hardly got any heatsink paste on it under the CPU cap.
If you dont suffer any strange heat related stability problems, I think its most likely that Coretemp isnt reading the temps properly.
Ignore it and use motherboard reported CPU temp.

ps coretemp values are not comparable with motherboard temp reported results.
The coretemp values are absolute values that have no calibration.