Service manual

1-14 AlphaServer GS80/160/320 Service Manual
1.7 Hierarchical System Architecture
AlphaServer GS80/160/320 systems are distributed shared-memory
multiprocessor systems with up to eight 4-processor QBBs inter-
connected by an 8x8 hierarchical switch (H-switch). The system
provides a single address space shared by all processors, though
memory is physically distributed over all nodes (QBBs) in the system.
1.7.1 The Primary Switch and the Quad Building Block
From an architectural point of view, the quad building block contains
the primary (local) switch connecting up to four CPUs, four memory
modules, and local I/O ports. If the system contains more than one
QBB, a secondary switch and further system support is required.
Figure 1– 7 Quad Building Block Block Diagram