I just recently came across this very detailed article all about Intel Core2 temperature readings. How the digital thermal sensors work, and don't work, how Intel is not very forthcoming with needed info, and so on:
http://www.tomshardware.com/fo.....ture-guide

Also, there is a pointer to a new temperature monitoring tool called RealTemp. They also have some interesting documentation on measuring Core thermals:
http://www.techpowerup.com/realtemp/docs.php