Comparison of real-time operating systems

This is a list of real-time operating systems (RTOSs). This is an operating system in which the time taken to process an input stimulus is less than the time lapsed until the next input stimulus of the same type.

Name	License	Source model	Target uses	Status	Platforms	Official website
Apache Mynewt	Apache 2.0	open source	embedded	active	ARM Cortex-M, MIPS32, Microchip PIC32, RISC-V	mynewt.apache.org
Arm OS	Apache 2.0				Cortex-M, Cortex-R, Cortex-A	os.mbed.com
BeRTOS	modified GNU GPL	open source	embedded	archived	ARM, Cortex-M3, ARM ARM7TDMI, Atmel AVR, PowerPC (emu), x86 (emu), x86-64 (emu)	www.bertos.org
CapROS	GNU GPL	open source	embedded	active	IA-32, ARM9	www.capros.org
ChibiOS/RT	Mixed, GNU GPL or proprietary	open source	embedded, small footprint	active	x86, ARM7, ARM9, Cortex-M0-M3-M4, PowerPC e200z, STM8, STM32, AVR, MSP430, ColdFire, H8S	www.chibios.org/dokuwiki/doku.php, sourceforge.net/projects/chibios
ChorusOS	?	?	?	defunct	SPARC, x86, PowerPC	docs.sun.com/app/docs/prod/chorus5
Concurrent CP/M, became MP/M	Proprietary	closed (meanwhile: open source)	general purpose, industrial	historic	8080, Z80, 8086	Digital Research
Concurrent DOS, became Multiuser DOS	Proprietary	closed		defunct	8086, 286, 386, 68000, (also 8080/Z80 in dual-processor variants)	Digital Research
Contiki	BSD	open source	embedded, WSN	active	MSP430, AVR, ARM	www.contiki-os.org
Data General RDOS	Proprietary	?	general purpose	defunct	Data General Nova, Data General Eclipse	?
Deos	Proprietary	closed	safety critical	active	x86, PowerPC, MIPS	www.ddci.com/products_deos.php
DioneOS	Proprietary	available for licensee	embedded		MSP430, MSP430x	www.elesoftrom.com.pl/en/os
DMERT (Duplex Multi-Environment Real-Time)	Proprietary (Bell Labs)	closed	OS for long-distance telephone switching systems	inactive	Bell Labs 3B20D (a proprietary, VAX-like system with redundant [duplex] processors)	?
DNIX	Proprietary	closed	general purpose	defunct	68000	?
GEC DOS	Proprietary	closed	process control	defunct	GEC 4000 series	?
DSOS	?	?	?	defunct	TI-980A minicomputer	?
DSP/BIOS	Free	closed, available with license	general purpose	maintenance only	Mostly Texas Instruments C2800, C5500, C6000 and OMAP DSP cores. Replaced by TI-RTOS, but available for download.	www.ti.com/tool/dspbios
DSPnano RTOS	Mixed, open source and commercial	open source	MCU, DSC, DSP SoC	active	R8C, M16C, PIC24, dsPIC33	www.rowebots.com/products/dspnano
eCos	Modified GNU GPL	open source	embedded		ARM-XScale-Cortex-M, CalmRISC, 680x0-ColdFire, fr30, FR-V, H8, IA-32, MIPS, MN10300, OpenRISC, PowerPC, SPARC, SuperH, V8xx	ecos.sourceware.org
eCosPro	Modified GNU GPL or eCosPro license	open source with non-free portions			ARM7-9, Cortex-A5-A9-M3-M4-M7, 680x0-ColdFire, H8-H8S, IA-32, MIPS32, MIPS64, microMIPS, NIOS II, OpenRISC, PowerPC, SPARC, SH4/4A, TILE-Gx, XScale	www.ecoscentric.com/ecos/ecospro.shtml
embOS	Proprietary	closed, available to customers, free object code for non-commercial use	embedded, industrial, IoT, safety critical	active	ARM7/9/11, ARM Cortex-A/R/M, AVR, AVR32, C16x, CR16C, ColdFire, H8, HCS12, M16C, M32C, MSP430, NIOS2, PIC18/24/32, R32C, R8C, RISC-V, RL78, RH850, RX100/200/600/700, RZ, SH2A, STM8, ST7, V850, 78K0, 8051	www.segger.com/embos.html
ERIKA Enterprise	GPL and GPL linking exception	open source	embedded		ARM7, ARM Cortex-M, ARM Cortex-A (on Jailhouse hypervisor), Hitachi H8, Altera Nios2, Microchip dsPIC (including dsPIC30, dsPIC33, and PIC24), Microchip PIC32, ST Microelectronics ST10, Infineon C167, Infineon Tricore, Freescale PPC e200 (MPC 56xx) (including PPC e200 z0, z6, z7), Freescale S12XS, EnSilica eSi-RISC, AVR, Lattice Mico32, MSP430, Renesas RX200, x86-64 (on Jailhouse hypervisor)	www.erika-enterprise.com
EROS	Modified GNU GPL	open source	experimental research use	dormant	IA-32	www.eros-os.org
FlexOS	Proprietary	closed	general purpose, industrial, POS	defunct	186, 286, 386, V60, V70, 68000	Digital Research, Novell
FreeRTOS	MIT	open source	embedded	active	ARM, AVR, AVR32, ColdFire, ESP32, HCS12, IA-32, Cortex-M3-M4-M7, Infineon XMC4000, MicroBlaze, MSP430, PIC, PIC32, Renesas H8/S, RISC-V, RX100-200-600-700, 8052, STM32, TriCore, EFM32	www.freertos.org
Fuchsia	Varies		embedded		AArch64, x86-64	fuchsia.dev
FunkOS	modified Sleepycat License		embedded		AVR, MSP430, Cortex-M3	funkos.sourceforge.net
HeartOS	Proprietary	closed	safety critical		x86, PowerPC, ARM	www.ddci.com/products_heartos.php
Huawei LiteOS	BSD	open source	embedded	active	ARM (M0/3/4/7, A7/17/53, ARM9/11), x86, RISC-V	www.huawei.com/minisite/liteos/en/about.html
IBM 4680 OS	Proprietary	closed	general purpose, industrial, POS	defunct	286	IBM (DR Concurrent DOS 286 derivative)
IBM 4690 OS	Proprietary			active	286, 386	IBM (DR FlexOS 286/386 derivative)
INTEGRITY	Proprietary		embedded		ARM, XScale, Blackfin, ColdFire, MIPS, PowerPC, x86	www.ghs.com/products/rtos/integrity.html
INtime	Proprietary				x86	tenasys.com/intime
ITRON	T-License	varies	embedded		ARM, MIPS, x86, Renesas RX100-200-600-700-others	www.tron.org
Kaspersky OS	Proprietary	open source	safety critical, virtualization	?	?	?
KolibriOS	GNU GPL	open source	embeddable	active	x86	www.kolibrios.org
LynxOS	Proprietary	source available	embedded		Motorola 68010, x86/IA-32, ARM, Freescale PowerPC, PowerPC 970, LEON	www.lynx.com/products/lynxos-178-do-178c-certified-posix-rtos
MenuetOS	GNU GPL	open source	?	active	IA-32	www.menuetos.net
MERT	Proprietary (Bell Labs)	closed	OS for long-distance telephone switching systems	inactive	PDP-11	?
MicroC/OS-III	Apache 2.0	open source	embedded		ARM7-9-11/Cortex-M1-3-4-A8/9, AVR, HC11/12/S12, ColdFire, Blackfin, MicroBlaze, NIOS, 8051, x86, Win32, H8S, M16C, M32C, MIPS, 68000, PIC24/dsPIC33/PIC32, MSP430, PowerPC, SH, StarCore, Renesas RX100-200-600-700, RL; STM32, …	weston-embedded.com/micrium/overview
MontaVista Linux	GNU GPL	open source	embedded	?		www.mvista.com
MP/M	Proprietary	closed (meanwhile: open source)	general purpose, industrial	defunct	8080, Z80, 8086	Digital Research
MQX	Proprietary	complimentary source available	embedded	active	Freescale Power, ColdFire, Kinetis Cortex ARM, List of Freescale products	www.freescale.com/mqx
Multiuser DOS	Proprietary	closed	general-purpose, industrial	defunct	386	Digital Research/Novell, Concurrent Controls, Datapac, IMS (see REAL/32)
Nano-RK	Mixed	open source	embedded, WSN	active	AVR, MSP430	www.nanork.org
Neutrino	Proprietary	some source provided	microkernel		ARM, ARM64, MIPS, PPC, SH, x86, x86-64, XScale	www.qnx.com/products/neutrino_rtos
Nucleus RTOS	Proprietary	source provided	embedded		ARM (Cortex-M3-M4-R4-R4F-A8-A9, ARM7-9-11), PowerPC, MIPS32-16e, microMIPS, ColdFire, SuperH	www.mentor.com/embedded-software/nucleus
NUT	Proprietary	open source	embedded, industrial		ARM-M0, ARM-M0+, ARM Cortex-M3, ARM9, ARM Cortex-M7, Cortex-M3	www.cedac.com
Nut/OS	BSD		embedded, industrial		AVR, AVR32, ARM7, ARM9, Cortex-M3	www.ethernut.de/en/firmware/nutos.html
NuttX	Apache 2.0	open source	embedded, small footprint		Linux user mode, ARM7-9, Cortex-A5-A8-A9-M0-M3-M4-M7, 8052, Espressif ESP32, Lattice LM32, Renesas MC16C/26/SH-1, RISC-V, Zilog Z16F, Zilog eZ80 Acclaim!, Zilog Z8Encore!, Z80, MIPS PIC32MX, PIC32MZ	nuttx.apache.org
OpenComRTOS	Proprietary	source provided	embedded		Freescale PowerPC, Texas Instruments C66xxx DSP, ARM, XMOS, MicroBlaze, LEON, NXP CoolFlux DSP, Melexis MLX16, Win32, Linux	www.altreonic.com
OS2000	Proprietary	?	embedded	active	MIPS (Baget variant), KOMDIV-32, KOMDIV-64, Intel BSPs (x86)	www.niisi.ru/otd07.htm
OS4000	Proprietary	closed	process control	maintenance only	GEC 4000 series	?
OSE	Proprietary	available to customers	general purpose	active	ARM, PowerPC, x86, TI OMAP, …	www.enea.com/ose
OS-9	Proprietary	available to customers	embedded		ARM-strongARM, MIPS, PowerPC, SuperH, x86/Pentium, XSCALE, Motorola 6809, 680x0, SPARC	www.microware.com
OSEK	Mixed, open source and commercial	specification			engine control units	Various (mostly Automotive) vendors implemented and distribute/sell OSEK
Phoenix-RTOS	BSD	open source	embedded	active	ARMv7 Cortex-M, ARMv7 Cortex-A, IA-32, RISC V	www.phoenix-rtos.com
PikeOS	Proprietary	available to customers	certifiable safety & security, embedded virtualisation		PPC, x86, ARM, MIPS, SPARC-LEON, RISC-V	www.sysgo.com/pikeos
Protothreads	BSD	open source	general purpose	active	Architecture independent	dunkels.com/adam/pt
pSOS	Proprietary	?	?	discontinued	680x0	?
QNX	Proprietary	?	general purpose, medical devices	active	IA-32, AMD64-32, MIPS, PowerPC, SH-4, ARM, ARM64, StrongARM, XScale	www.qnx.com
QP	Dual, open source and commercial	dual	MCU, DSC, DSP SoC		ARM7/9, ARM Cortex-M3-M0, MSP430, TMS320C28x, AVR, AVRXmega, ColdFire, 68HC08, M16C/R8C, H8, 8051, 80251, PIC18, PIC24/dsPIC33, Nios II, PSoC1	www.state-machine.com/qp
REAL/32	Proprietary	closed	general-purpose, industrial		386	IMS (Multiuser DOS derivative)
Real-time Linux (CONFIG_RT_PREEMPT)	GNU GPLv2	open source	general purpose		same as Linux	www.osadl.org/Realtime-Linux.projects-realtime-linux.0.html, rt.wiki.kernel.org, wiki.linuxfoundation.org/realtime/start
RedHawk Linux RTOS	Proprietary	closed	hardware-in-the-loop, software-in-the-loop, general purpose	active	Intel, AMD, ARM, NVIDIA Drive, NVIDIA Jetson Orin	www.concurrent-rt.com
REX OS	Proprietary	closed, available with license	embedded	inactive	ARM	ja:REX OS
RIOT	GNU LGPL	open source		active	ARM, MSP430, AVR, x86, RISC-V	www.riot-os.org
RMX	Proprietary	closed		defunct	Intel 8080, 8086, 80386, higher	tenasys.com/rmx
RODOS	BSD	source provided		active	ARMv7 (M3, A8, A9), AVR32, PowerPC 405, SPARC64 Platforms: SmartFusion2, RaspberryPi, STM32 On an OS: Linux, Windows, macOS, FreeRTOS, RTEMS	rodos download
RSX-11	Proprietary	?	?	historic	PDP-11	n/a
RT-11	Proprietary	?	general purpose	defunct	PDP-11	n/a
RTAI	GNU GPL	open source	general purpose	active	x86 (with and without FPU and TSC), x86-64, PowerPC, ARM (StrongARM; ARM7: clps711x-family, Cirrus Logic EP7xxx, CS89712, PXA25x), m68k (supporting both MMU and NOMMU cpus)	www.rtai.org
RTEMS	modified GNU GPL		embedded		ARM, Blackfin, ColdFire, TI C3x/C4x, H8/300, x86, 68k, Milkymist SoC, MIPS, Nios II, PowerPC, SuperH, SPARC, ERC32, LEON, Mongoose-V	rtems.com
RTLinux	GNU GPL		general purpose	inactive	same as Linux	Official vendor Wind River Linux
RT-Kernel	Proprietary	source provided	embedded	active	ARM, Blackfin	rt-labs.com/product/rt-kernel/
RT-Thread	Apache 2.0	open source	embedded	active	ARM, ARM Cortex-M0-M3-R4-M4-M7, IA-32, AVR32, Blackfin, nios, PPC, M16C, MIPS (loongson-1b-1c, PIC32，xburst), MicroBlaze, V850, unicore32,	code.google.com/p/rt-thread, www.rt-thread.org
RTXC Quadros	Proprietary	source available	embedded		ARM - Atmel/Freescale/NXP/ST/TI, Blackfin, 680x0-ColdFire, PowerPC, StarCore, TI-Luminary Stellaris, TI OMAP, XScale	www.quadros.com/products/operating-systems
RTX, RTX64	Proprietary	closed	MS Windows extension		x86, x86-64	RTX64 RTOS, Real-Time Solutions for Windows 10 IoT (intervalzero.com)
RX116	?	?	embedded, industrial	defunct	NEC V20, NEC V30, NEC V40, NEC V50	first ITRON 1 compatible 16-bit RTOS
RX616	?	?	safety critical, embedded, industrial		NEC V60, NEC V70	32-bit ITRON compatible
RX-UX832	?	?	embedded, industrial, general-purpose		NEC V60, NEC V70	32-bit Unix-like RTOS
SafeRTOS	Proprietary	source code & Design Assurance Pack available	embedded, safety critical	active	Same as FreeRTOS	Same as FreeRTOS
SHaRK	GNU GPL	open source	?	inactive	?	shark.sssup.it
Simulink Real-Time	Proprietary	closed	real-time testing-embedded	active	x86	www.mathworks.com/products/simulink-real-time
SINTRAN III	?	?	?	?	Norsk Data computers	n/a
Symbian OS	Eclipse	open source	embedded	defunct	ARM	www.symbian.org
T-Kernel	T-License	source available	embedded RTOS	active	ARM, MIPS, SH, more	www.tron.org
THEOS	?	?	?	?	?	www.theos-software.com
ThreadX	Proprietary	partial source available	?	active	ARC, ARM/Thumb, AVR32, BlackFin, 680x0-ColdFire, H8-300H, Luminary Micro Stellaris, M-CORE, MicroBlaze, PIC24-dsPIC, PIC32, MIPS, V8xx, Nios II, PowerPC, Renesas RX100, RX200, RX600, RX700, Synergy, SH, SHARC, StarCore, STM32, StrongARM, TMS320C54x, TMS320C6x, x86/x386, XScale, Xtensa/Diamond, ZSP	azure.microsoft.com/en-us/services/rtos
TI-RTOS Kernel (SYS/BIOS)	BSD	open source	embedded		Mostly Texas Instruments: MSP430-432, C2000-5000-6000, TI's ARM families (Cortex M3-4F-R4-A8-A15), SimpleLink Wireless CC2xxx-CC3xxx	www.ti.com/tool/sysbios
Transaction Processing Facility	Proprietary	mixed	general purpose	active	IBM Z series	www.ibm.com/products/z-transaction-processing-facility
TRON project	Free	mixed	mixed	active	any: is a specification, not an implementation	www.tron.org
UNIX-RTR	?	?	?	defunct	PDP-11	?
UNOS	?	?	?	historic	680x0	?
µITRON	T-License	open source	embedded	active	ARM, MIPS, x86, Renesas RX100-200-600-700-others	www.tron.org
u-velOSity	Proprietary	?	microkernel	active	?	www.ghs.com/products/micro_velosity.html
velOSity	?	?	?		Power ISA, ARM/XScale, MIPS, x86/Pentium, ColdFire, Blackfin, OMAP, DaVinci	www.ghs.com/products/velosity.html
VAXELN	Proprietary	closed source	?	historic	VAX
VRTX	Proprietary	?	?	superseded by Nucleus RTOS	ARM, MIPS, PowerPC, RISC	www.mentor.com/embedded-software/nucleus
VxWorks	Proprietary	?	embedded	active	ARM, IA-32, Intel 64, MIPS, PowerPC, SH-4, StrongARM, xScale	www.windriver.com/products/vxworks
Windows CE	Proprietary	Microsoft Shared Source			x86, MIPS, ARM, SuperH	www.microsoft.com/windowsembedded
Windows 10 IoT	Proprietary	?			Intel Atom, Celeron, Pentium; Qualcomm Snapdragon, Broadcom, NXP i.MX	www.microsoft.com/en-us/windowsforbusiness/windows-iot^[1]^[2]
Xenomai	GNU GPLv2	open source	general		x86, x86-64, PowerPC, ARM, Analog Devices Blackfin BF52x, BF53x, BF54x and BF56x	www.xenomai.org
XINU	Free		embedded	active	x86, MIPS, ARM, AVR	xinu.cs.purdue.edu
XMK	BSD	embedded	inactive-beta	?	www.integerfox.com/xmk
Zephyr	Apache 2.0	open source	embedded	active	ARM (Cortex-M0, -M3, -M4, -M23, -M33, -R4, -R5, -A53), x86, ARC, RISC-V, Nios II, Xtensa, SPARC	www.zephyrproject.org

References

1. "Windows Processor Requirements". docs.microsoft.com.
2. "Windows for Internet of Things (IoT) Platforms & Applications". Microsoft Windows for Business.

External links

• Comparison of real-time operating systems at Curlie