Using The Nonmaskable Interrupt (Nmi) Button - Silicon Graphics Origin200 Owner's Manual

Chapter 4: Operating an Origin200 System
78

Using the Nonmaskable Interrupt (NMI) Button

The nonmaskable interrupt is similar to reset, except that the system's current state is
saved. When you press the nonmaskable interrupt button, this is referred to as
"generating a nonmaskable interrupt" or "NMI."
Generating an NMI is can be useful when attempting to solve application and system
problems that cause the system to halt. If you experience problems with your system or
an application, your support provider may instruct you to generate an NMI in order to
recover data or examine the system.
To generate an NMI, press the NMI button. (See Figure 4-1). What happens when you
generate an NMI depends upon the state of the system at the time:
• If the system was running in PROM mode, the CPU immediately enters power-on
diagnostics (POD) mode.
• If a kernel debugging facility (such as symmon) is available, the system may start
that utility.
• If the kernel debugging facility fails due to data corruption, you can generate a
second NMI and force the system into POD mode.
You can also generate an NMI using a module system controller command. See "Using
the AUX Port and Module System Controller Commands."
Occasionally, a system may not respond to an NMI. If this happens, you can either press
the reset button or turn the system off and on again.