Preparing the System

Before a real-time program executes, you must set up the system in the following ways.

Choose the CPU or CPUs that the real-time program will use. CPU 0 (at least) must be reserved for IRIX system functions.
Decide which CPUs will handle I/O interrupts. By default, IRIX distributes I/O interrupts across all available processors as a means of balancing the load (referred to as spraying interrupts). CPUs that are used for real-time programs should be removed from the distribution set (see "Assigning Interrupts to CPUs").
Make sure that none of the real-time CPUs is managing the clock (see "Assigning the Clock Processor"). Normally the responsibility of handling 10ms scheduler interrupts is given to CPU 0.
Make sure none of the real-time CPUs is handling the fast timer ("Assigning the fasthz Processor"). This responsibility is typically given to CPU 0 along with all other housekeeping.

Each Frame Scheduler takes care of restricting and isolating its CPU, so that the CPU is used only be processes scheduled by the Frame Scheduler.