Silicon is ("mostly") EM speed on a microscopic waffer. If thats to be protected, somesthing faster would be awesome, but we dont have that yet so we are limited at using something that is at least equally fast and try do our best. So by necesity silicon is required to protect silicon. Nothing else works. If there are fuses and other devices those will be subordinated, meaning silicon will trigger and control them. If there is a fuse it only works coz there is silicon somewhere that buys it time to blow it on purpose. But the fuse alone cant work. Ptc or others even less so. Because all these are based on effects of the current passing through, that means current has to pass through first for the effect to take place. So by definition of their causality effect, they are too slow. Miliseconds range, tens or hundreads are for fuses. The silicon time domain is in nanoseconds scale. That means in the same time a flameable fuse blows, IC may blow a thousand times.
Its "mostly" EM and not fully so, only mostly because of parasitic capacitance associated to silicon junction and also dissipation requirements. This is why processors had to go for lower voltages, now are stuck to smth like 4-5 Ghz freq and we have multicores instead of single core. If we had technology to make switches with no parasitic effects and zero losses then we would all have truly speed of light processors that would be single core and would never need to be upgraded.
Its "mostly" EM and not fully so, only mostly because of parasitic capacitance associated to silicon junction and also dissipation requirements. This is why processors had to go for lower voltages, now are stuck to smth like 4-5 Ghz freq and we have multicores instead of single core. If we had technology to make switches with no parasitic effects and zero losses then we would all have truly speed of light processors that would be single core and would never need to be upgraded.