The value that is used is determined by the type of interrupt that occurred. State information is stored, depending on the machine architecture, the operating system and whether the interrupt is interrupting the servicing of another interrupt. When the interrupt service routine is finished, state information is restored, depending on the machine architecture. A special instruction is executed that loads the old value of the PC into the PC, and the processor mode is changed to user mode. Since these resources will be allocated for a long time, this is a significant advantage for a long-running session.
Response time is faster for threads than for processes.
Since the session is with an end-user, this is a significant advantage. In addition, the time for a context switch and the throughput are not, in themselves, important concerns in this case. The context switch time is only relevant to the extent that it improves the response time.