Technical data

20
Chapter 2: Chassis Tour
Board Configuration and Layout
There is a direct correlation between the number of Node boards that are installed and
the number of XIO slots that can be activated.
If a system module has only one Node board, then only six of the twelve XIO slots are
activated. When two Node boards are installed, all twelve of the XIO slots can be
activated, if the Node boards are positioned in the correct slots.
Figure 2-3 diagrams the Node board-to XIO board correlation. The Node boards and
their corresponding XIO board slots are indicated with either a circle or triangle. When
Node 1 is present, IO slots 1 through 6 (designated by a circle) are activated. When
Node 2 is also present, then IO slots 7 through 12 (designated by a triangle) are activated.
20. PDU switch The PDU switch is the main circuit breaker for the entire rack
assembly.
21. Node board The Node board is the main processing board in the SGI 2400
or 2800 system. It contains one or two 64-bit CPUs, the hub
(which provides an interface to the I/O subsystem and the
CrayLink Interconnect), a portion of main memory, as well as
directory memory. Each node board can support from 64 MB
to 4 GB of memory. A single-rack system can have between one
to eight Node boards. A multiple-rack system can have up to
64 Node boards.
22. BaseIO board This board provides basic I/O functions for the system, such as
serial ports, (fast) Ethernet, and single-ended wide SCSI.
A dedicated slot in the XIO cardcage houses the BaseIO board.
This board cannot be installed in any of the other XIO
expansion slots.
23. XIO slot cardcage The XIO cardcage allows you to install additional I/O boards
in the SGI 2400 and 2800 chassis.
24. XIO cable guide The XIO cable guide management helps to ensure proper
laying out of cables in the rear of the chassis.
25. Module power switch These switches power on and off the individual modules.
Table 2-1 (continued) SGI 2400 and 2800 Major Components
Component Description