Comparison of real-time operating systems explained

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		Source model	Target uses !	Status	Platforms
Apache Mynewt			open source	embedded	active
BeRTOS		open source	embedded	archived	ARM, Cortex-M3, ARM ARM7TDMI, Atmel AVR, PowerPC (emu), x86 (emu), x86-64 (emu)
CapROS		open source	embedded	active
ChibiOS/RT		open source	embedded, small footprint	active	x86, ARM7, ARM9, Cortex-M0-M3-M4, PowerPC e200z, STM8, STM32, AVR, MSP430, ColdFire, H8S
				defunct	SPARC, x86, PowerPC
		closed (meanwhile: open source)	general purpose, industrial	historic	8080, Z80, 8086
		closed	general purpose, industrial	defunct	8086, 286, 386, 68000, (also 8080/Z80 in dual-processor variants)
		open source		active	MSP430, AVR, ARM
			general purpose	defunct
		closed	safety critical	active	x86, PowerPC, ARM, MIPS
		available for licensee	embedded	active	MSP430, MSP430x
DMERT (Duplex Multi-Environment Real-Time)	(Bell Labs)	closed	OS for long-distance telephone switching systems	inactive	Bell Labs 3B20D (a proprietary, VAX-like system with redundant [duplex] processors)
		closed	general purpose	defunct	68000
GEC DOS		closed	process control	defunct	GEC 4000 series
		closed		defunct	TI-980A minicomputer
		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.
DSPnano RTOS		open source	MCU, DSC, DSP SoC	active	R8C, M16C, PIC24, dsPIC33
eCos		open source	embedded	inactive	ARM-XScale-Cortex-M, CalmRISC, 680x0-ColdFire, fr30, FR-V, H8, IA-32, MIPS, MN10300, OpenRISC, PowerPC, SPARC, SuperH, V8xx
		open source with non-free portions	embedded	active	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
		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
ERIKA Enterprise		open source	embedded	active	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)
EROS		open source	experimental research use	dormant	IA-32
		closed	general purpose, industrial, POS	defunct	186, 286, 386, V60, V70, 68000
Flexible Safety RTOS		closed, available to customers	embedded, safety critical	active	Altera/Intel NIOS II, ARM9, ARM Cortex-M, ARM Cortex-R, ARM Cortex-A, Infineon TriCore, Infineon AURIX, NXP ColdFire, NXP Kinetis, NXP PowerPC e200, NXP QorIQ, STMicroelectronics STM32, Xilinx/AMD MicroBlaze
FreeRTOS		open source	embedded	active
		open source	embedded
		open source	embedded		Arm Cortex-M
FunkOS		open source	embedded		AVR, MSP430, Cortex-M3
		closed	safety critical		x86, PowerPC, ARM
Huawei LiteOS		open source	embedded	defunct	ARM (M0/3/4/7, A7/17/53, ARM9/11), x86, RISC-V
		closed	embedded	active	AArch64, x86-64, RISC-V, LingxiISA
		closed	general purpose, industrial, POS	defunct	286
			general purpose, industrial, POS	active	286, 386
			embedded		ARM, XScale, Blackfin, ColdFire, MIPS, PowerPC, x86
			embedded		x86
ITRON		varies	embedded		ARM, MIPS, x86, Renesas RX100-200-600-700-others
Kaspersky OS		open source	safety critical, virtualization		x86, x86_64, ARMV5, ARMV7, ARMV8, MIPS32
KolibriOS		open source	embeddable		x86
LynxOS		source available	embedded		Motorola 68010, x86/IA-32, ARM, Freescale PowerPC, PowerPC 970, LEON
		open source	embedded		Arm Cortex-M
MenuetOS		open source			IA-32
	(Bell Labs)	closed	OS for long-distance telephone switching systems	inactive
MicroC/OS-III		open source	embedded	active	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, ...
		open source	embedded
		closed (meanwhile: open source)	general purpose, industrial	defunct	8080, Z80, 8086
M-RTOS		closed	safety critical, embedded	active	PowerPC, ARM, MIPS
		complimentary source available	embedded	active
		closed	general-purpose, industrial	defunct	386
		open source		defunct	AVR, MSP430
		some source provided	microkernel, embedded, industrial	active	ARM, ARM64, MIPS, PPC, SH, x86, x86-64, XScale
Nucleus RTOS		source provided	embedded		ARM (Cortex-M3-M4-R4-R4F-A8-A9, ARM7-9-11), PowerPC, MIPS32-16e, microMIPS, ColdFire, SuperH
NUT		open source	embedded, industrial		ARM-M0, ARM-M0+, ARM Cortex-M3, ARM9, ARM Cortex-M7, Cortex-M3
		open source	embedded, industrial		AVR, AVR32, ARM7, ARM9, Cortex-M3
		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
		source provided	embedded
			embedded	active	MIPS (Baget variant), KOMDIV-32, KOMDIV-64, Intel BSPs (x86)
		closed	process control	maintenance only	GEC 4000 series
OSE		available to customers	general purpose	active	ARM, PowerPC, x86, TI OMAP, ...
		available to customers	embedded		ARM-strongARM, MIPS, PowerPC, SuperH, x86/Pentium, XSCALE, Motorola 6809, 680x0, SPARC
		specification	embedded		engine control units
Phoenix-RTOS		open source	embedded	active	ARMv7 Cortex-M, ARMv7 Cortex-A, IA-32, RISC V
		available to customers	certifiable safety & security, embedded virtualisation	active	PPC, x86, ARM, MIPS, SPARC-LEON, RISC-V
Protothreads		open source	general purpose	active	Architecture independent
				discontinued	680x0
		royalty-free licensing	embedded	active	Embedded MCU and MPU architectures. ARM's Cortex-M, Cortex-R, Cortex-A, RISC-V. AMP and SMP configurations.
			microkernel, embedded, industrial		active
		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
		closed	general-purpose, industrial		386
Real-time Linux (PREEMPT RT)		open source	general purpose		x86, x86_64, RISC-V, ARM64 and LoongArch (ARM and POWER in the -rt branch)^[1]
RedHawk Linux RTOS		closed	hardware-in-the-loop, software-in-the-loop, general purpose	active	Intel, AMD, ARM, NVIDIA Drive, NVIDIA Jetson Orin
		closed, available with license	embedded	inactive	ARM
		open source		active	ARM7, ARM Cortex M, MSP430, AVR, RISC-V, Xtensa
		closed		defunct	Intel 8080, 8086, 80386, higher
		source provided		active	ARMv7 (M3, A8, A9), AVR32, PowerPC 405, SPARC64Platforms: SmartFusion2, RaspberryPi, STM32On an OS: Linux, Windows, macOS, FreeRTOS, RTEMS
				historic	PDP-11
			general purpose	defunct	PDP-11
		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)
			embedded	active	AArch64, ARM, Blackfin, ColdFire, TI C3x/C4x, H8/300, x86, x86_64, 68k, Microblaze, Milkymist SoC, MIPS, Nios II, PowerPC, SuperH, SPARC, ERC32, LEON, Mongoose-V
			general purpose	inactive
RT-Kernel		source provided	embedded	active	ARM, Blackfin
RT-Thread		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,
		source available	embedded		ARM - Atmel/Freescale/NXP/ST/TI, Blackfin, 680x0-ColdFire, PowerPC, StarCore, TI-Luminary Stellaris, TI OMAP, XScale
		closed	MS Windows extension		x86, x86-64
			embedded, industrial	defunct
			safety critical, embedded, industrial
			embedded, industrial, general-purpose		NEC V60, NEC V70
		source code & Design Assurance Pack available	embedded, safety critical	active
SHaRK		open source		inactive
		closed	real-time testing-embedded	active	x86
					Norsk Data computers
Symbian OS		open source	embedded	defunct	ARM
T-Kernel		source available	embedded RTOS	active	ARM, MIPS, SH, more

		open source		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
TI-RTOS Kernel (SYS/BIOS)		open source	embedded	active	Mostly Texas Instruments: MSP430-432, C2000-5000-6000, TI's ARM families (Cortex M3-4F-R4-A8-A15), SimpleLink Wireless CC2xxx-CC3xxx
		open source	embedded	active
Transaction Processing Facility		mixed	general purpose	active	IBM Z series
TRON project		mixed	mixed	active	any: is a specification, not an implementation
				defunct
				historic	680x0
UniProton		open source	embedded	active	AArch64 (Kunpeng), x86-64 on openEuler community & ARM, RISC-V, x86, x64 and LoongArch on OpenHarmony and Oniro OS as add-on kernel
μITRON		open source	embedded	active	ARM, MIPS, x86, Renesas RX100-200-600-700-others
			microkernel	active
				active	Power ISA, ARM/XScale, MIPS, x86/Pentium, ColdFire, Blackfin, OMAP, DaVinci
		closed source		historic	VAX

			embedded	active	ARM, IA-32, Intel 64, MIPS, PowerPC, SH-4, StrongARM, xScale
		Microsoft Shared Source			x86, MIPS, ARM, SuperH
					Intel Atom, Celeron, Pentium; Qualcomm Snapdragon, Broadcom, NXP i.MX
		open source	general		x86, x86-64, PowerPC, ARM, Analog Devices Blackfin BF52x, BF53x, BF54x and BF56x
		open source	embedded	active	x86, MIPS, ARM, AVR
		open source	embedded	inactive
Zephyr		open source	embedded	active

External links

2024 RTOS Performance Report (FreeRTOS / ThreadX / PX5 / Zephyr) - Beningo Embedded Group
2013 RTOS Comparison (Nucleus / ThreadX / ucOS / Unison) - Embedded Magazine

Notes and References

https://wiki.linuxfoundation.org/realtime/preempt_rt_versions PREEMPT_RT patch versions