CPU Temperature required for auto-shutdown

Max CPU temp is entirely dependent on the model of CPU. The manufacturers make these values readily available on the spec sheets and white papers for each CPU. Most aftermarket motherboards have the ability to choose which temperature an overheat shutdown occurs at. Most vendor-supplied boards (from Dell, HP, whatever) have this feature locked at the recommended value for the CPU that ships with the computer.

Personally I consider 70C to be the red line cross, especially for AMD CPUs, which are said to be more vulnerable to overheat.

One thing is certain: 105C is absolutely too much.