IBM Enterprise System/900 Type 9121 system controller and memory subsystem design

A system controller supporting two processors, two independent memory banks, and a channel subsystem has been implemented within a single air-cooled thermal conduction module for the IBM Enterprise System/9000™ Type 9121 processors. Improvements in technology densities, usage of CMOS and emitter-coupled logic on the same substrate, and innovations in the system controller design were required to achieve the one-module objective. In addition, system reliability is improved with a storage key error-correction code, and storage allocation options are increased with a combined main/expanded store design. In conjunction with the system controller development, a new memory subsystem has been designed for the 9121 system. Innovative large-system memory packaging techniques and functional changes in the data accessing methods have culminated in a memory board which supports up to one-gigabyte system storage.