Processing overhead of the RISC state-swapping operation in the ISDN software processing

The processing overhead of the reduced instruction set computer (RISC) state-swapping operation is evaluated in the ISDN software environment. A model for the ISDN application tasks is introduced to simulate the processing of ISDN user-network interface protocols. A simple approach is developed to arrive at an estimate for this overhead. The measurement of the processing was calculated for two ISDN applications tasks, the Q.931 basic call control and the TEI assignment. The overhead cost was measured in relation to the total memory references and to the total machine instruction processing time. Results show that this overhead is significant, and is especially so if the number of ISDN messages being processed during task execution is small