The IBM S/390(R) fifth-generation CMOS-based server (more commonly known as
the G5) produced a dramatic improvement in system-level performance in com
parison with its predecessor, the G4, Much of this improvement can be attri
buted to an innovative approach to the cache and memory hierarchy: the bino
dal cache architecture. This design features shared caching and very high s
ustainable bandwidths at all points in the system. It contains several inno
vations in managing shared data, in maintaining high bandwidths at critical
points in the system, and in sustaining high performance with unparalleled
fault tolerance and recovery capabilities, This paper addresses several of
these key features as they are implemented in the S/390 G5 server and its
successor, the S/390 G6 server.