However, the observations above and further inspection of the LC3 diagram led us to design a different approach to the simulation of this system. The fundamental notion in our Pull– Model approach is that at any point in time, only a small fraction of the computed outputs for the devices is actually relevant and necessary for the logic to perform correctly. Consider the effect of the signal GateMARMUX set to zero. This means that the input to that tri–state buffer is irrelevant. Transitively,that further means that the inputs to the MARMUX are not relevant, as is the input to the zero–extender ZEXT connected to the MARMUX. Similarly, when the GatePC signal is also zero, the contents of the PC register, the inputs of the PCMUX, and both of the ADDRMUX multiplexers are meaningless. Finally, consider the effect of GateMARMUX set to one, and MARMUX.SEL set to zero (selecting the leftmost input of the multiplexer). In this case, the rightmost input (corresponding to a selector of one) is meaningless, as are all signals feeding that input transitively. Clearly, expending simulator CPU cycles to determine the value of signals which ultimately are unused is inefficient.