|There may be settings in the BIOS (setup screens) to control when and how the CPU fan runs. |
I would guess the heat sink may be installed wrong. As I stated above, the thermal rating of that processor is only 8W. Not very much at all. I am wondering if the fan is running at all.
I couldn't find the proper technique for your processor but I am guessing it is to apply a small dot and then spread it using a business card or similar.
Artic silver is one of the best thermal compounds you can buy.
As mentioned above, be sure the vents are clear and use the unit on a flat, hard surface.
You are correct to be concerned about the 90c temperatures. You are reading in Celsius aren't you?