Optimizing a semiconductor wafer fab requires balancing technology and productivity. Recent work on productivity modeling will be described and focus on discrete event simulation models of unitary tool, modules, and whole fab. In addition, some related cost-modeling aspects will be presented. The Applied Materials Turbo Modules Environment is reviewed. Turbo-Modules Unitary Tool Models (UTM) were developed for determining a configured tool's performance, and the Tool Group Models (TGM) were developed for exploring module and fab modeling. Turbo-Modules is based on AutoSimulations, Inc. (ASI) AutoSched AP's open architecture and a customized Graphical User Interface (GUI). The presentation provides a case study performed to analyze the loss of accuracy in a tool group model by modeling unitary tools as black box. Some fab cost modeling will be discussed.