Here is what I think is going on. Yes speedfan and asus read some on die reading - idle/load jumps very quickly to confirm this. However, the difference between speedfan and Coretemp on most machines is ~ 13-16c with coretemp being hotter. My theory (just a hunch) is that speedfan and the motherboard temp programs are simulating a Tcase value. Yes they are reading ON DIE in the core, but you can manipulate values with this to simulate Tcase - I do believe there is a relationship between Tcase and Tjunction and it can be simulated although probably not a linear relationship. Of course, it is not a TRUE Tcase value as the only way to get this is to cut a channel in the IHS and place a probe in the center of the IHS. Coretemp and the Intel Thermal Analysis Tool I believe are reading the DTS at is raw value, meaning both programs are just displaying what the DTS is telling them. Again, there is no INSOCKET thermistors with C2D.