There is a direct correlation between the number of Node boards installed in the system's compute module and the number of XIO slots that can be activated.

If a system compute module has only one Node board, then only 6 of the 12 XIO slots are activated. When two Node boards are installed, all 12 of the XIO slots can be activated, if the Node boards are positioned in the correct slots.

Figure 2-5 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, XIO slots 1 through 6 (designated by a circle) are activated. When Node 2 is also present, then XIO slots 7 through 12 (designated by a triangle) are activated.

Node boards 3 and 4 also have corresponding XIO slots indicated by a circle or a triangle. For example, if Node boards are installed in slot 1 and slot 3, then only the corresponding XIO slots (1 through 6) are activated.

Figure 2-5. Block Diagram for the Compute Module (Single Rack)

Figure 2-6. Block Diagram for the Compute Modules (Multirack System)

Note that the graphics BaseIO interface board assembly uses one of the XIO slots. Various types of optional interface boards are supported in the XIO slots. These may include:

Certain installation restrictions must be followed when XIO boards are installed or removed. Failure to follow these configuration rules may result in system or peripheral malfunction.

Always ensure these XIO rules are followed:

Never allow any of these configurations:

Node board slots are counted from right to left. Router board and XIO board slots are counted from left to right. Refer back to Figure 2-5 for a diagram of the back of the compute module that differentiates the supported XIO slots. The circles and triangles represent the interdependence of the XIO slots and the Node boards that support them.

The graphics BaseIO panel assembly (also known as the IO6G) installs in XIO board slot one and is used to connect external devices to the system. These devices include keyboards, mice, SCSI devices, audio devices, ASCII terminals, printers, and modems. The I/O panel configuration is shown in Figure 2-7.

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Note: If you disconnect a cable from a peripheral device, you should also disconnect it from the I/O connector on the I/O panel. This helps prevent the system from picking up external electrical noise. Connectors are listed in Table 2-3.

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Figure 2-7. Graphics BaseIO Panel (IO6G)

The 64-bit processor (CPU) is the main processor for the Onyx2 graphics rack system. There are two 64-bit CPUs on each Node board. You may hear a module or rack system referred to as an “8P” or “16P” system. The P stands for processor. An 8P system has eight 64-bit processors (four Node boards). The 64-bit processor is also called a microprocessor.

The Node boards in the Onyx2 use SDRAMs mounted on dual-inline memory modules (DIMMs) for main memory. A Node board can have from 64 MB to 4 GB of main memory. Memory upgrades are available in 64, 128, and 512 MB increments.

The HUB on the Node board is the primary communication link between the 64-bit processor(s), the I/O subsystem, the main memory, and the CrayLink Interconnect. The HUB also interfaces with directory memory, which is responsible for maintaining cache coherence.

Figure 2-9 shows the outer panel on the Node board. The 18 LEDs provide status information for the individual boards. Two red LEDs are located near the top of the board and a set of 16 yellow ones are located near the middle of the board.

The two LEDs near the top of the board should light only when there is a voltage inconsistency or problem on the Node board. If these LEDs light up frequently, the board may need service. If all the top LEDs on all the Node boards in the system light up, it indicates a system wide power problem. In this case, call your service representative for assistance.

The LEDs grouped near the middle of the board are divided into two vertical sets of eight LEDs (16 total). Each vertical set of eight LEDs represents one of the 64-bit microprocessors installed on the Node board. When only one microprocessor is installed, you can expect to see LED activity on only one vertical set of LEDs.

As a general rule, the bottom LEDs should always show some activity while the system is powered on. The bottom LEDs serve as a kind of “heartbeat” that indicates when a microprocessor is working, even if the system is not generally active. The other seven LEDs light up as the processes that the microprocessor runs increase. The more it is active, the more amber LED activity you see on the Node board.

Figure 2-9. Node Board LEDs

The MSC and its LED display provide environmental and status monitoring for an individual compute module. Each compute and graphics module in a graphics rack system reports its information to the “multimodule” controller (also known as the MMSC).

The multimodule controller (MMSC) display (see Figure 2-10) is the single-point administration interface for the rackmount configuration. The individual module controllers are tied to the multimodule controller through a serial connection from the module to the multimodule controller board in the rack.

The MMSC color screen display interface and MMSC logic unit are two separate components.

There is only one MMSC display interface per rack system configuration. It acts as the single point of administration for all compute modules in the rack configuration. In addition, in a multirack configuration, the rack with the MMSC and display should always be placed in the leftmost position.

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Caution: The MMSC front panel display provides a convenient method to power on, shut down, reset, and issue a nonmaskable interrupt (NMI) to the entire rack configuration. Use extreme care when issuing these commands from the display. Make sure that all affected users are notified before a system wide command is executed.

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Figure 2-10. MMSC Interface and Display Panel

The Null router provides a low-cost method to connect two Node boards in a module. The Null Router board cannot be used for CrayLink Interconnect linking, and it does not have any external router connectors. The Null router board is generally used in deskside systems with only one or two Node boards.

The Star Router is always paired with a Rack Router board for proper operation. This cost-effective router board provides connections with all the Node boards in a module but cannot be used for CrayLink Interconnect linking. The Star Router has one external connector which connects to a port on the companion CrayLink Interconnect router board through a jumper. The Star Router board is generally used in a single-rack Onyx2 graphics system that uses three or four Node boards and does not require connection to additional compute modules.

The Rack Router boards provide CrayLink Interconnection in a multirack Onyx2 system that uses more than one compute module. This Router board can support configurations with up to 64 processors. The Rack Router has six ports that route data at up to 800 MBps (per port). Three of the ports connect internally. The fourth, fifth, and sixth ports can connect to external router ports on other compute modules.

The CrayLink Interconnect and the Xpress Links are the cabled interface that runs between rack Router boards (see Figure 2-12). These cables provide a high speed (800 MBps), scalable interconnection between different modules. These cables also supply physical link redundancy so that if a link fails, another link can take its place.

Figure 2-12. Crosstown and CrayLink Interconnect Cables

The crosstown cables connect each graphics module's KTOWN interface board directly with the compute module. Each pipe in the graphics module must have its own crosstown cable connection coming from a crosstown XIO board in the compute module. The KTOWN board in the graphics module sits directly between the two board sets in the graphics module.

Cautionary Guidelines

You generally should not handle these sensitive linking cables; they are very delicate. Observe the following guidelines if you need to move these cables:

• Avoid bending the cables tighter than a 1.25-inch (3.2 cm) radius.

• Avoid stepping on the cables.

• Avoid “hot plugging” in or removing cables while the system is up and running. This can hang or crash the entire graphics rack system.

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Caution: Additional Router and crosstown cable connections should be performed only by Silicon Graphics-certified personnel.

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