External clocks

The QNX Neutrino RTOS can be driven with an external clock. In some systems there's a "standard" clock source supplied as part of the system or of the highly integrated CPU chip itself. For convenience, the OS can operate with an external clock source that's not generated by this component. However, keep two things in mind:

Therefore, keep the rates down to a reasonable number. Almost all modern processors can handle clock interrupts at 1 kHz or lower — processors with higher CPU clock rates (e.g. Pentium-class, 300 MHz RISC processors, etc.) can handle faster clock interrupts.

Note that there's no requirement to keep the clock frequency to some "round number." If it's convenient to derive the clock interrupt from a baud rate generator or other crystal, the OS will be able to accurately scale the incoming clock rate for use in its internal timers and time-of-day clocks.