Faulty temperature sensor?

[Mr Wolf]

Hi to all!
I have a Toshiba Satellite Pro P300 notebook, with Mobile Intel Core 2 Duo T8300.
My problem is: when I use applications which I think require a large GPU usage, for example when I play Doom 3, or even use programs as Google Earth or Stellarium, after a while the fan goes at the maximum speed and, if don't exit the application, the PC turns it off brutally. I think there's a sort of "protection mechanism".
I don't know if this is directly related to GPU, since this also occurs when I boot the PC from a boot cd, or even when I enter the BIOS: the fan, after a while, even if the PC was cold, goes at the maximum speed and the PC turns it off.
This thing has always happened since I bought the PC: the fan always went at the maximum speed, but previoulsy the PC didn't turn it off.
During the "normal" use of the PC, for example, just surfing on the internet, but even using applications which require an intense CPU usage, as Matlab, the fan never goes at the maximum speed, neither after many hours of use.
With Core Temp, the temperature during the "normal" use is about 50° for both the cores, while, when for example playing Doom 3, it reaches about 70°, and the fan starts to turn fast. But the odd thing is that, after I close Doom 3, the temperature immediately goes down to about 60°.
It can't be the temperature goes down of 10° in a few seconds, as it can't be the fan starts to turn fast just entering the BIOS, so could it be the temperature sensor faulty?

Thanks in advance for your help!

[The Coolest]

This is how temperature sensors work.
When you stop the workload, the processor stops producing heat rapidly, and so the temperature drops.
It also enters a lower power state, which reduces heat output to a minimum level, thus makes the cool off period of the core much quicker.

CPUs and GPUs both contain temperature thresholds where they will automatically cut power to the machine.
If the GPU does not receive proper cooling and overheats, it might not impact your CPU temperature in a noticable manner. My suggestion is to try an application which will display the GPU temperature as well and see how hot the GPU is actually getting.

[viper_carl]

My BIOs Has a setting for that! I believe it's the over temp protection (Cool and Quiet)! I turned the target temp to the lowest and my fan starts speeding up @ 40 C! This cooled down the cpu by 10 C(From 62 C AMD MAX) ! All heavy graphics use large amounts of CPU and this causes heat! I went to a liquid cooler and running @ 29-39C! Hope this helps !