IBM Power 780 Technical Overview And Introduction page 76

To allow such concurrent maintenance operation, plugging the SMP Flex cables in the order
of their numbering is extremely important. Each cable is numbered, as shown in Figure 2-11.
Note that the 2- and 3-Drawer cabling has changed in this model.
Figure 2-11 SMP cables installation
Figure 2-12 and Figure 2-13 shows the changed SMP cabling for 2- and 3-drawer
configurations. There is some overlap of the cables, so some are hidden from view.
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IBM Power 770 and 780 (9117-MMD, 9179-MHD) Technical Overview and Introduction