High-power linear accelerators have potential applications in fusion materials testing, intense spallation neutron production for neutron physics, production of nuclear materials and destruction of nuclear waste. Determining the optimal configuration and operating parameters for the accelerator early in the design process is an important step in minimizing development costs associated with these applications. A coordinated evaluation capability in the rf system and other major supporting subsystems would thus provide a fully integrated system design. Further, characterizing component redundancy where necessary to provide a specified facility/system on-line availability completes a highly representative engineering and costing configuration. The Accelerator System Model (ASM) code provides this unique capability for developing optimum designs. ASM has been under joint development of computer interface, physics and engineering activities for four years and now permits the detailed layout and evaluation of a wide variety of normal and superconducting accelerator and rf power configurations for the aforementioned devices and other accelerator applications. This paper describes the current capabilities of the latest version of ASM, details continuing concentration on an integral reliability/availability approach, new component development and support system models.