An apparatus and method for computing event timing for high speed event based test system. The event processing apparatus includes an event memory for storing event data of each event where the event data includes timing data for each event which is formed with an integer multiple of a clock period and a fraction of the clock period, an event summing logic for accumulating the timing data and producing the accumulated timing data in a parallel form, and an event generator for generating events specified by the event data based on the accumulated timing data received in the parallel form from the event summing logic. The events in the event data are specified as groups of events where each group of event is configured by one base event and at least one companion event.