The NitrOS-9 docs say it is a process based multitasking environment, and that it is a real time OS (RTOS). But I'm not sure if that means it's preemptive (OS takes control away from a program/process to give others time to run) or if the program needs to play nice and relinquish the CPU like you might see in Windows 3.1.


Yes, it is pre-emptive. See: https://sourceforge.net/p/nitros9/wiki/The_Kernel/#multiprogramming

In particular, it uses the 60 Hz interrupt to switch between active processes with the same priority.

As a side note, some of the Color Computer I/O devices are CPU intensive (e.g., the bit-banger serial port and the floppy drive). This makes the system rather unresponsive when those devices are in use.

  • 2
    Yes, this is real-time in that it has a real-time clock (as well as a regular clock). It is not real time in terms of guarantees on consistent amounts of time for servicing tasks.
    – user12
    Jun 20 '16 at 20:01
  • Thus the no-halt controller e.g. Disto, and of course a proper RS-232 port. Aug 10 '16 at 9:34

OS-9, which NitrOS-9 is based on, could be either pre-emptive or not. If not, context switches could occur when the currently running process did a system call. To be pre-emptive, there has to be a source of periodic interrupts and a module, clock, with an interface that lets the OS use said source.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.