NEC ACOS System 550

This was a large general-purpose computer developed as the high-end model of the ACOS Series. To cope with the increasing diversity of processing in large systems, process concepts were extended for use with multiprocessors, and dispatching control, time slice control and input/output control were written into firmware. Overhead was reduced by using segmentation and paging concepts in input/output processing. The S550 was a completely symmetrical system where any CPU could simultaneously access any memory unit or input/output unit,and that with no bottlenecks. This machine achieved high-performance and high-reliability using the same LSI technology as the S350 and S450.