xpyrofuryx, the following is from the Core 2 Quad and Duo Temperature Guide:
http://www.tomshardware.com/forum/221745-29-core-quad-temperature-guide
Your question is answered toward the end of the paragraph.
Section 8: Tools
Note 3: SpeedFan is very flexible and is the temperature monitoring utility of choice. SpeedFan detects and labels thermal sensors according to various motherboard, chipset and super I/O chip configurations, so the
Tcase label can be CPU, Temp 1, Temp 2, or Temp 3. Even if
Tcase is labeled as CPU, it is still necessary to confirm the identity of
Tcase prior to conducting
Calibrations. Run Prime95 and note which SpeedFan temperature scales with an Idle to Load Delta similar to the Cores. This will identify the label corresponding to
Tcase. Labels can later be renamed using the
Configure button, (see
Section 11). If a temperature shows a flame icon, this indicates alarm limits which require adjustment. Use the
Configure button to set CPU and Core temp alarms to
Safe Scale. If a temperature shows
Aux 127, this is simply an unassigned input which can be disabled using the
Configure button. CPU`s with Steppings which are
Tjunction Max
100c typically require +
15c Core
Offsets. See
Section 11.
Comp