IBM pSeries 690 Service Manual page 58

Placement of Subsystem 4 in a Two-Rack Configuration (Rear View
with IBF)
C1 Primary Rack
C2 Secondary Rack
1 First I/O Subsystem
2 Second I/O Subsystem
Note: The physical location shown for I/O Subsystem 4 is populated only when IBFs are present and four
or more I/O subsystems are installed.
42 Eserver pSeries 690 Service Guide
3 Third I/O Subsystem
4 Fourth I/O Subsystem
4B Four IBFs