Isn't it the same for all core 2 cpu's, what's already been said, that they look at the difference in temp from core temp to tjunction temp, but intel haven't published what these tjunction values are. It is just an assumption from any temp monitoring software what this tjunction value is. On the original post, Realtemp is assuming 95 whereas coretemp is assuming 105, which is why there is exactly a 10c difference between the two. On the version of coretemp I'm using at the moment, it's assuming a tjunction of 100c for my q6600.
What we really need is for intel to publish these figures, or have them coded onto each cpu, so that they can be identified by the temp monitoring software.