Semiconductor wafer fabrications are very complicated systems, known as re-entrant flow shop. They are often modeled as open/closed queueing networks to estimate their performance indicators, such as cycle time, throughput and so on. In this paper, we first extend MVA, which is a method of estimating cycle time in closed queueing networks, to queueing networks with multiple servers and priority. Then we evaluate the influence of hot lots on a cycle time of ordinary lots. By incorporating the cost estimation method proposed by Iwata et al., we also propose the cost estimation methods of hot lots.
