Abstract
The author discusses the development of the VLSI-/370 microprocessor, especially the top-down verification process mainly based on the multilevel design verification system presented by W. Roesner (1988). The focus is on the functional design verification, which is based on various simulation processes. A major objective is to start the verification process as early as possible, long before the design is complete. This objective is important also for microcode and testcase development. To achieve this goal, a set of specification languages for different levels of abstraction has been developed in order to generate and simulate models composed even of mixes of these levels.<>