IBM AS/400 processor technology

The architecture of the IBM AS/400 processor has unique silicon performance and density requirements which are addressed with 12.7 mm CMOS ASIC chips utilizing 0.8 μm lithography and 0.5 μm channel lengths. The I/O performance and high simultaneous switch requirements for the processor are resolved with a high performance, ceramic, multi-chip module and digital slope controlled off-chip drivers. Four phase clocks are implemented to meet functional requirements. The system clock skews were minimized through a distributed phase-lock-loop and an automated procedure to balance clocks on the logic chips. The larger processor to I/O device distance requirements led to the implementation of a serial fiber optic link as the I/O bus extender. The underlying requirements for all of the technologies utilized in the AS/400 were high quality and high productivity