Technical data

1.15 Backplanes
Different backplanes are used in the BA430/BA440 Enclosures; backplane
54–20181–01 is used in the BA430 and backplane 54–19354–01 is used in
the BA440 enclosure.
1.15.1 BA430 Backplane (54–20181–01)
The BA430 backplane contains connectors for DSSI and SCSI busses. This
40.7 cm x 52.1 cm (16.0 inch x 20.5 inch) 4-layer backplane contains two
signal layers, one power layer and one ground layer.
Figure 1–19: BA430 Backplane
Mass Storage
Connectors
Module
Connectors
Power Supply
Connectors
MLO-005359
1.15.2 BA440 Backplane (54–19354–01)
The BA440 enclosure has a 12-slot, quad-height backplane (Figure 1–20).
The backplane is a 52.5 x 40.7-cm (21 x 16-in) assembly. The space between
each backplane slot varies. The backplane’s printed circuit board is an 8
layer, 2 sided etch board.
From right to left, the first five backplane slots are for the memories and
CPU, while the other seven slots are Q22/CD bus slots.
The Q-bus can be extended using, an enclosure expander unit. The BA430/
BA440 enclosure supports 35 equivalent ac loads and 20 dc loads from
all the modules installed in the backplane. An ac load is the amount of
capacitance a module presents to a bus signal line. One ac load equals
1–26 BA430/BA440 Enclosure Maintenance