We present a system-level technique to analyze the impact of design optimizations on system-level timing dependencies. This technique enables us to speed up the design cycle by substituting, in the design the loop, the time-consuming simulation step with a fast timing update routine. As a result, we can significantly reduce the design time from on the order of hours/days to the order of seconds/minutes. The update algorithm is defined on the Transaction Level Model (TLM) and can be used by any design flow that invokes TLM-based optimizations. This algorithm has lineartime complexity in the program size and experimental results indicate that any loss of accuracy due to this technique is negligible (<