AT&T 3B2 Maintenance Reference Manual page 175

Version 3
When reinstalling a BuBus board, carefully place it into the edge guides. Gently slide it in
until
it
touches the backplane connector. Make sure that both edges of the board are resting in
the card guides. Apply even pressure on both sides of the faceplate as you press the board
into the connector.
Processor Bus (PBus) Boards
The CM518C system board and CM519B backplane provide the processor bus (PBus) in place
of the uBus. The PBus occupies the three slots on the left hand side of the backplane, directly
underneath the system board. These slots are numbered from top down, starting with zero.
Since the PBus borrowed one slot from the BuBus, only three BuBus slots are provided by this
backplane. See Figure 6-16 for layouts of the backplanes.
The PBus, like the uBus, provides unbuffered access to the CPU bus on the system board. This
bus is used exclusively by the processing element (PE) boards.
The PE board (CM524A) works only in conjunction with a CM518C system board. Also,
Release 2 of the multiprocessor enhancement (MPE) software must be installed (the same
package used for the MPB board). A 3B2/1000 Model 80 comes equipped with one PE board.
This board is not required for system operation. If it is defective, it may be removed until a
replacement board is available. The system will run slower without the PE installed.
Although this board is named differently from the MPB, the 3B2 identifies either board by the
same name, namely, mph. For instance, the output of the
prtconf
command will show mpb
for either an MPB board in a BuBus slot or a PE board in a PBus slot. The output will show,
however, on which bus the board is located. The same thing is true for the equipped device
table (EDT). The EDT will also show the slot number and occurrence (count) for each mpb.
When running diagnostics on either an MPB board or PE board, the device name supplied
should be
mpb.
To run diagnostics on a single board when more than one is installed, it is
necessary to supply the number of the mph board. The system will number the MPB and PE
boards starting with the BuBus slots 0-2, and then the PBus slots 0-2. Figure 6-16 shows an
example. In this example, if the first PE board (the one in slot 0 of the PBus) is to be
diagnosed, the command would be: dgn mph= 1. Specific phases may also be specified.
382 Subassemblies
6-35