NEC ACOS Series 77 System 200

The S200 was developed to have the optimal architecture for a small computer, and to employ common hardware technology with the higher-end System S300, S400 and S500. Firmware technology was adopted as the control system for the central processing unit, and LSI and MSI were actively used in the main memory and logic circuits. The system incorporated microdiagnosis capability and system reconfiguration capability as countermeasures against failures, and had improved operation performance and source/program and data file compatibility with the S300, S400 and S500. 1K N-channel MOS LSI (18 pins) was used as the memory element in the main memory, and 1K write-controllable PROM was used as the memory element in ROS (Read Only Storage) in a read only memory unit for storing firmware.