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Message Queue eXecutive (MQX)
DeveloperDy4 Systems, Inc.
Precise Software Technologies, Inc.
ARC International
Synopsys, Inc.
Embedded Access, Inc.
Working stateCurrent
Source modelClosed source
Initial release1991; 33 years ago (1991)
Latest release5.2 / May 2022; 1 year ago (2022-05)
Marketing targetEmbedded systems: industrial, medical, consumer
Available inC, assembly language (ASM)
PlatformsKinetis, ColdFire, PowerPC, ARC, ARM, StrongARM, xScale
Kernel typeMicrokernel RTOS
Preceded byMPX (renamed Harmony)

MQX (Message Queue eXecutive) is a real-time operating system (RTOS) developed by Precise Software Technologies, Inc., and currently sold by Synopsys, Embedded Access, Inc., and NXP Semiconductors.

Like most RTOSs, MQX includes a multitasking kernel with pre-emptive scheduling and fast interrupt response, extensive inter-process communication and synchronization facilities, and a file system.

Its configurable size conserves computer memory space using a minimum of 6 KB of read-only memory (ROM), including its kernel, interrupts, semaphores, queues, and a memory manager.

MQX includes an Internet protocol suite TCP/IP stack (RTCS), embedded File Allocation Table based DOS file system (MFS), Universal Serial Bus (USB) host/device stack, and design, debugging (task-aware (TAD), and remote), and performance analysis tools.[1] It is supported by popular libraries for Secure Sockets Layer (SSL) and Transport Layer Security (TLS) such as wolfSSL for increased security measures.

MQX is generally used in embedded systems. MQX development occurs on a host machine running Unix or Windows, and cross-compiles target software to run on various target central processing unit (CPU) architectures.

MQX has been ported to many platforms and now runs on most modern CPUs used in the embedded market, including Kinetis, ColdFire, PowerPC, ARC, ARM, StrongARM, xScale.

All new Kinetis (ARM Cortex-M4), i.MX RT (ARM Cortex-M7), and ColdFire devices will be enabled with complimentary Freescale MQX RTOS. Freescale plans to expand the availability of this complimentary integrated enablement software to include many embedded processors in its broad portfolio.


MQX had its origins at Dy4 Systems, Inc., a company based in Ottawa, Canada. In 1984, a small team of software engineers there, consisting of Jeremy James, Mati Sauks, and Craig Honegger started researching novel applications for embedded multiprocessors. This work led to the use of a real-time operating system in writing firmware for Dy4 single board computers. In 1989, James and Sauks commercialized the Harmony RTOS, with the name MPX, which was developed for portable multiprocessor real-time computing systems by the National Research Council Canada, and created a company named Precise Software Technologies, Inc.

This effort led to developing the Precise Real-Time Executive technology that was the basis of a product named MQX and MQX+m, which were real-time executives for single processor and multiprocessor applications. The unique asynchronous message passing paradigm delivered by MQX when it was introduced in 1991 and the royalty-free licensing model were accepted immediately in the embedded real-time market. Since the introduction of MQX, Precise continually added functions to the MQX RTOS69 through its various iterations and versions.

Precise Software Technologies was acquired by ARC International in March, 2000[2] and continued to develop, license and sell MQX on many new processor architectures including Freescale ColdFire, IBM/Freescale PowerPC and ARM. In 2004, Embedded Access assumed distribution and support of the MQX RTOS on non-ARC processor architectures. In 2009, Freescale began shipping the MQX RTOS complimentary with selected ColdFire MCUs.

MQX has been used in thousands of embedded projects by over 1,000 companies, who have shipped millions of products running it. Today, firms such as ABB, Agilent, ATI Technologies, Baoruh Electronic, Bausch and Lomb, General Dynamics, Daewoo, Exabyte, General Electric, B.F. Goodrich, Liebert, Matrox, Mitel Networks, Philips, Porsche, QLogic, SICK, Sony, Tyco, and Xerox use MQX in applications such as industrial control, networking, storage, and consumer electronics.


  1. ^ "Freescale MQX Software Solutions". Retrieved 2012-03-07.
  2. ^ "ARC Cores acquires two small IP vendors". Retrieved 2012-09-04.