Service manual

System Overview 1-5
Figure 1–2 shows a QBB backplane and its connectors. Module locations are
identified by callouts.
48V/Vaux power connector (present only on even numbered QBBs in the
rear of the system)
Global port module connector (note there are two backplanes: the one for
the front QBB has the global port connector on its back facing the rear of
the cabinet and the one for the back QBB has the global port connector on
its front also facing the rear of the cabinet.)
Directory module connector (necessary if a system has more than one
QBB)
CPU module connectors (up to four)
Memory module connectors (up to four)
Local I/O riser module connectors (up to two with two ports each)
48V/Vaux power input connectors
Cutout in backplane
Short-circuit protection module (will be designed into the backplane later)
Clock splitter module connector
11
Power system manager module connector
12
Main power module connector
13
Auxiliary power module connector
QBBs are placed such that their global ports are as close to each other as is
possible. Global ports are the second-level switches through which CPUs in one
QBB communicate with CPUs and memories in other QBBs. In fact, global
ports have to be physically close to each other to enable fast second-level
switching. This requires that QBB backplanes be flipped when placed in a
system box. Therefore, the orientation of the backplane is important and
determines the location of modules. See Section 4.4 for QBB and module
orientations.
Figure 1–2 shows the orientation of the backplanes in QBBs 5 and 7.