Technical data

2-32 Diagnostic Procedures
Return to the default debug settings by simultaneously pressing the Menu and Scroll
Down buttons while cycling the key switch.
Cycle the key switch to return to normal controller operation.
2.5.3.4 Communicating With a Disabled Processor
When a processor fails, it is disabled by the system. Because a disabled processor is unable
to talk to the system bus, you cannot use IDE to diagnose the cause of the fault. Enable the
processor by first turning the key switch to the Manager position. Select the Debug Settings
menu and set the No Diagnostics bit. Power cycle the system to activate the change to the
debug settings menu and enable the faulty processor. See Section 4.5.2, “Key Switch in the
Manager Position,” for additional information on the Debug Settings menu.
2.5.4 Using a Debug Kernel to Find System Hangs
The following describes how to make and use a debug kernel to help diagnose system
hangs. With a debug kernel, the debugger symmon boots along with the kernel when the
system is started.
Follow these steps to create and boot a debug kernel:
1. Set the system console to the serial port using the PROM monitor.
2. In /var/sysgen/system/irix.sm, find the line with idbg. Change EXCLUDE to INCLUDE.
3. Go to the end of the file and remove the asterisk (*)from the CCOPTS line containing
-XNp, and add an asterisk (*) to the other CCOPTS line
4. Remove the asterisk (*) from the LDOPTS line containing -T 80100000, and add an
asterisk (*) to the other LDOPTS line. Note that CCOPTS and LDOPTS lines are paired.
This causes the kernel to be shifted in memory to make room for the debugger.
5. Run the command autoconfig from the command line.
6. Boot this kernel. It should automatically bring in symmon.
Allow the machine to hang; induce it if the hang is repeatable, or run the system until the
hang occurs. When a hang occurs, follow these steps to use the debug kernel:
1. When the hang occurs, press <Ctrl>-A on the serial console. You should see the
following prompt:
DBG:
If there is no response when you press <Ctrl>-A on the system console, use the front
panel of the System Controller to issue a nonmaskable interrupt (NMI).
If there is a DBG: prompt on the console, press <Ctrl>-A again and continue with the
next step.
If issuing an NMI does not place the system in debug mode (no DBG: prompt is
displayed), you cannot continue. Issue a second NMI to place the system in POD
mode, from which you can use further diagnostics as described in Chapter 5, “PROM
Monitor.”