IBM RS/6000 SP Handbook page 325

Each type (size) of node occupies one slot or a consecutive sequence of slots.
For each node, there is an integer n such that a thin node (or Expansion I/O unit)
occupies slot n, a wide node occupies slots n and n+1, and a high node occupies
n, n+1, n+2 and n+3. For single thin nodes (not in a pair), wide nodes, and high
nodes, n must be odd. For an SP-attached server and a Clustered Enterprise
Server, n is 1. Use n in place of slot_number in the formula.
Node numbers are assigned independent of whether the frame is fully populated.
Figure 10-9 demonstrates node numbering. Frame 4 represents an SP-attached
server in a position where it does not interrupt the switched frame and
companion non-switched expansion frame configuration. It can use a switch port
on Frame 2, which is left available by the high nodes in frame 3. Frame 4's node
number is determined by using the previous formula.
16
15 31
13 14
29
12
11 27
10
9 25
7 8 23
5 6
21
3 19
4
2
1 17
SP Switch SP Switch
Frame 1 Frame 2
Figure 10-9 Node numbering in an SP system with SP-attached server
Switch port numbering
In a switched system, the switch boards are attached to each other to form a
larger communication fabric. Each switch provides some number of ports to
which a node can connect (16 ports for an SP Switch and 8 ports for the SP
Switch-8). In larger systems, additional switch boards (intermediate switch
boards) in the SP Switch frame are provided for switch board connectivity; such
boards do not provide node switch ports.
Switch port numbers are used internally in PSSP software as a direct index into
the switch topology and to determine routes between switch nodes.
If an SP System or a CES System has an SP Switch, Switch port number (also
known as switch node number) is calculated by switch number and port number:
switch_port_number = ((switch_board_ number - 1) x 16) + port_number
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41
39
37
35
33
Frame 3
Node 49
Frame 4
Chapter 10. Clustering configurations
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89
85
81
SP Switch
Frame 6
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