Periodic process load control system

A periodic process load control system for use in a multiple-process operating system comprises an activation event generation unit 10 for periodically generating events to activate a periodic process, the process comprising a soft real time process portion D which selectively executes or omits non-essential processings B, C or changes their frequency of execution according to an accumulation value of a plurality of past time intervals between a previous operating time and the current time from which the loading of the processor is determined. The accumulation value is compared with threshold values (Figure 10) for high and low loads and the processing selected accordingly to minimise degrading the frequency of execution of a real time process A when the system is highly loaded.