Demand Driven Simulation: BACKSIM

A new digital simulation algorithm is presented based on the concept of demand driven simulation. Where traditional event driven simulation propagates signal values forward through a circuit in response to input pin events, demand driven simulation propagates requests for simulation values backwards both through the circuit and through time. In this manner, only those evaluations required to obtain "watched" signal values are performed. BACKSIM, the simulator based on this algorithm, has proven to be faster and more efficient than event driven simulation for every test case tried to date.