Extension Nodes - IBM RS/6000 SP Handbook

Frames have locations known as drawers into which the processor nodes are
mounted. Tall frames have eight drawers and short frames have four. Each
drawer location is further divided into two slots. A slot has the capacity of one thin
node or SP Expansion I/O unit. A wide node occupies one full drawer, while a
high node occupies two full drawers. The maximum number of SP frames
supported in an SP system is 128.
Note: The Model 555 is a tall frame with an integral SEPBU power supply,
and SP Switch (F/C 4011), but no processor nodes. This frame provides node
interconnectivity to CES systems having configurations of 2 to 16 servers. You
must add an SP Expansion Frame (F/C 1550) containing an SP Switch for
configurations of 17 to 32 servers.
For more information, refer to Chapter 4, "Frames" on page 139.

1.4.3 Extension nodes

An extension node is a non-standard node that extends the SP system's
capabilities but that cannot be used in the same manner as a standard node.
Note that SP systems with extension nodes require PSSP Version 2.3 or later.
One type of extension node is a dependent node. A dependent node depends on
SP nodes for certain functions but implements much of the switch-related
protocol that standard nodes use on the SP Switch. Typically, dependent nodes
consist of four major components as follows:
1. A physical dependent node: The hardware device requiring SP processor
node support.
2. A dependent node adapter: A communication card mounted in the physical
dependent node. This card provides a mechanical interface for the cable
connecting the physical dependent node to the SP system.
3. A logical dependent node: It is made up of a valid, unused node slot and the
corresponding unused SP Switch port. The physical dependent node logically
occupies the empty node slot by using the corresponding SP Switch port. The
switch port provides a mechanical interface for the cable connecting the SP
system to the physical dependent node.
4. A cable: It connects the dependent node adapter with the logical dependent
node. It connects the extension node to the SP system.
A specific type of dependent node is the SP Switch Router (9077-04S and
9077-16S models). It is a licensed version of the Lucent GRF switched IP router
that has been enhanced for direct connection to the SP Switch. The SP Switch
router uses networking cards (Ethernet, FDDI, ATM, Sonet, HIPPI, HSSI) that fit
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