Deterministic Response
External event and timings dictate the request of service.
OS’s response depends on the speed at which it can respond to interrupts and on whether the system has sufficient capacity to handle requests.
Determinism is concerned with how long the OS delays before acknowledging an interrupt.
In non-RT this delay may be in the order of 10’s and 100’s of millisecs, whereas in an RT it may have an upper-bound of few microsec to 1millisec.