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Real Time Operating Systems QNx RTOS 6.1. Professor: Mohamed Khalil CSE 8343 GROUP-A1 Anita Kanuganti. Agenda. Overview Features Examples of RTOS QNx RTOS v 6.1 System Architecture Task Handling Method Memory Management Method Interrupt Handling Method Internet Support

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Real time operating systems qnx rtos 6 1

Real Time Operating SystemsQNx RTOS 6.1

Professor: Mohamed Khalil

CSE 8343


Anita Kanuganti


  • Overview

  • Features

  • Examples of RTOS

  • QNx RTOS v 6.1

    • System Architecture

    • Task Handling Method

    • Memory Management Method

    • Interrupt Handling Method

    • Internet Support

    • Most widely used Tools

    • Positive & Negative points


  • References

Real time systems
Real time systems

  • “Real-time computing is computing where system correctness depends not only on the correctness of the logical result of the computation but also on the result delivery time”

Real time operating systems rtos
Real time operating systems(RTOS)

  • A good RTOS can be defined as one that has a bounded (predictable) behavior under all system load scenarios (simultaneous interrupts and thread execution.

Rtos features
RTOS Features:

  • Small Footprint

  • Preemptible

  • Multi-architecture

  • Predictable response times to electronic events


  • QNx

  • VxWorks

  • Windows NT

  • Windows 2k

  • Linux

  • Linux/RT

Introduction to qnx rtos v 6 1
Introduction to QNx RTOS v 6.1

  • QNx is a RTOS from QNx Software Systems Ltd

  • Commercial POSIX-compliant OS

  • Designed for embedded systems

  • Contains micro-kernel,internet software, including a web browser and server, embeddable graphical user interface, comprehensive software library

Qnx system architecture
QNx System Architecture

Micro-kernel Architecture:











Hardware Interrupt




Cont d qnx system architecture
Cont’dQNx - System Architecture

  • True client-server architecture

  • Message-based OS

  • Supports SMP and high availability features

  • Advantages:

    • Robustness

    • Reliable

  • Disadvantage:

    • Overhead caused by memory protection

  • Task handling method
    Task Handling Method

    • Processes & Threads

    • Scheduling Policies

      • Prioritized FIFO

      • Round – Robin scheduling

      • Adaptive

      • Sporadic

    Memory management method
    Memory Management Method

    • Virtual memory supported by paging mechanisms of processor

    • Swapping disk enabled by “unlock” calls

    • Demand paging not implemented due to real time nature

    • Full virtual memory protection

    • Physical page size is 4k

    Interrupt handling method
    Interrupt Handling Method

    • Interrupt handled in nested and prioritized fashion

    • Interrupt service routine(ISR) runs in the context of the thread that attached it

    • ISR has its own stack

    • Interrupt to task communication through signals and pulses

    Internet support
    Internet Support

    • Voyager Web Server: an HTTP server to serve web pages

    • Voyager Web Browser for viewing information

    • Voyager SDK to build internet enabled applications

    Most widely used tools
    Most widely used Tools

    • Metrowerks Codewarrior IDE

    • GCC Toolkit

    • Photon developer’s toolkit to develop photon user interfaces

    • TCP/IP toolkit

    Qnx rtos v6 11

    Positive points

    Fast and predictable

    Excellent architecture for distributed Robust systems

    Good Platform support

    Negative points


    QNx RTOS v6.1


    • The system can be seamlessly distributed over several nodes, and is network transparent

    • True client-server architecture which improves its robustness and reliability

    • System’s performance is fast and predictable

    • As opposed to the earlier versions of QNx RTOS, which only supported the Intel x86 family of processors, version 6.x also supports MIPS, PowerPC, StrongARM and SH4


    • “Real-Time Systems & Software” Alan C. Shaw.