IBM pSeries 7311 D10 Service Manual page 23

Four I/O Subsystems, Eight I/O Subsystems: The illustration on the left shows four I/O subsystems
connected to the processor subsystem using one SPCN loop. The illustration on the right shows eight I/O
subsystems connected to the processor subsystem using one SPCN loop.
Processor Subsystem Connected to Four or Eight Model D10 I/O Subsystems:
RIO Cabling
I/O subsystems are connected to the processor subsystem through remote I/O (RIO) cable loops. The
cable loops are connected to ports that are on the rear of the processor subsystem. The RIO cables are
connected in loops so that the system has two paths to each I/O subsystem when more than one I/O
drawer is in a loop.
If only one I/O subsystem is in a RIO loop and both the processor subsystem and the I/O subsystem are
RIO-2 capable, the RIO-2 cables are used as one two-cable path to the I/O subsystem. In this cable
configuration, the data rate is increased by a factor of 2.
v A maximum of eight Model D10 drawers are supported on one processor subsystem.
v If both D10 I/O drawers are connected to the same processor subsystem, the total number of I/O
subsystems supported is eight.
v The maximum number of I/O subsystems supported on one RIO loop is four.
v The D10 I/O drawers must be on separate RIO loops.
v The speed at which a RIO loop operates is set by the capability of the drawers on the loop. If the
system is capable of operating at RIO-2 speed, but any drawer on the same loop is capable of RIO
speed, the whole loop operates at RIO speed.
The system can have up to four RIO loops. A total of eight I/O drawers can be connected to the processor
subsystem in a variety of cabling configurations. For optimum performance, connect the RIO loops in a
configuration that distributes multiple I/O drawers among as many RIO loops as possible. A dedicated RIO
loop for each I/O drawer can provide optimum performance. Some examples of valid cabling examples
follow.
1 Processor Subsystem
2 I/O Subsystem
Chapter 1. Reference Information
7