The machine architecture and design considerations for an interrupt-driven bipolar VLSI Microprocessor are presented. The processor is designed to a complex architecture and includes an integrated channel and a flexible storage interface. Floating-point functions are optional. A 3-ns custom bipolar technology was developed for the microprocessor, resulting in a very high circuit density package. The 50-mm four-chip air-cooled microprocessor module is packaged on a printed-circuit card with associated repowering circuits and high-speed random-access memory. Important design considerations and tradeoffs associated with the development of this machine, within specific cost, performance, reliability, and schedule objectives, are discussed. Various processor design techniques are described which minimize hardware where performance is not critical. A degree of functional parallelism is utilized, as well as timing flexibility, to attain the required performance.