How Hot Are You? Determine the Temperature of Your Core Duo

As it was already the case for G3, most of G4 and G5 processors, the Core Duo features internal probes delivering information related to the temperature of the CPU.
However, it seems that apple does not use them to optimize the cooling system of the MacIntel. OSX is using other probes located at different points in the machine, as well as the CPU usage, to evaluate the temperature of components and control fans to keep the overall hardware as cool as possible. So Apple did not develop an extension able to collect information/register from CPU probes.
Some users have decided to develop such extension, its name SpeedIt that can downloaded from http://speedit.increw.org
Once downloaded, place the extension in your user account (root level), and via the terminal enter the following command lines (validate and enter your password when required)
sudo chown -R root:wheel speedit.kext
then
sudo kextload -v speedit.kext
Then to know the temperature of the CPU simply enter the following command line:
sysctl kern.cpu_temp
Tested with a MB Pro 2.16GHz, this application reported 50°C when the MB Pro was not used, and 90C when CPU usage was 100%. When reaching 9°0C, fan starts to spin to actively cool down the dual core CPU.
If you send request rapidly to know the CPU temperature, you might experience some huge variation of the reported data, the Core Duo might have one probe per core. In addition a third probe is also there to shut down the CPU in case of fast overheating; but it does not have any register, it is a basic fuse.
PS: This extension is supposed not only temperature, but also other CPU-related information such as clock speed; but in our test, only the temperature could be retrieved.
[update] according to Core duo specifications, this CPU is designed to run at temperature up to 100°C. The safety probe/fuse shut it down if the temperature reaches 125°C.