Microprocessors are already embedded in Aircrew Training Devices (ATDs) for display generation, input/output control, and other special purpose applications. This paper deals with the key factors relating to the use of microprocessor systems (rather than minicomputers) in performing the central computational function for ATDs. Such factors include key performance parameters to be considered when replacing a 32-bit minicomputer by a system of microprocessors; requirements for a recent Air Force ATD system; benchmarks for computational performance; and specific changes to ATD prime item development Specifications.