Comparison of real-time operating systems

This is a list of real-time operating systems. An RTOS is an operating system in which the maximum time from an input stimulus to an output response can be definitely determined.

Name	License	Source model	Target usage	Status	Platforms	Official site
Ardence RTX	proprietary	closed	MS Windows extension	active?	x86	[1]
ARTOS (Locamation)	proprietary	?	embedded	active	x86	[2]
ARTOS (Robotu)	proprietary	?	embedded	active	ARM9+	[3]
AVIX	proprietary	closed	embedded	active	PIC24F, PIC24H, dsPIC30F, dsPIC33F, PIC32MX	[4]
BeRTOS	modified GNU GPL	open source	embedded	active	DSP56K, I196, IA32, ARM, AVR	[5]
ChibiOS/RT	Modified GNU GPL	open source	embedded, small footprint	active	x86, ARM7, ARM Cortex-M0, ARM Cortex-M3, PowerPC e200z, STM8, AVR, MSP430, Coldfire, H8S	[6] [7]
ChorusOS	?	?	?	?	?	[8]
CMX RTOS	proprietary	?	embedded	active	IA32, ARM, AVR, H8, PIC, 8051	[9]
Contiki	BSD	open source	embedded	active	MSP430, AVR	[10]
COS	proprietary	closed	process control	defunct	GEC 4000 series	?
Deos	proprietary	closed	safety critical	active	x86, PowerPC, PowerQUICC	[11]
DNIX	proprietary	closed	general purpose	defunct	68000	?
GEC DOS	proprietary	closed	process control	defunct	GEC 4000 series	?
DrRtos	free?	open?	?	active?	ARM7	[12]
DSPnano RTOS	Open Source and Commercial	Open Source	MCU, DSC, DSP SoC	active	R8C, M16C, PIC24, dsPIC33	[13]
DSOS	?	?	?	defunct	TI-980A minicomputer	?
eCos	modified GNU GPL	open source	general purpose	active	ARM/XScale, CalmRISC, 68000/Coldfire, fr30, FR-V, H8, IA32, MIPS, MN10300, OpenRISC, PowerPC, SPARC, SuperH, V8xx	[14]
eCosPro	modified GNU GPL and eCosPro license	open source with non-free portions	general purpose	active	ARM/XScale, CalmRISC, 68000/Coldfire, fr30, FR-V, H8, IA32, MIPS, MN10300, NIOS2, OpenRISC, PowerPC, SPARC, SuperH, V8xx	[15]
embOS	proprietary	closed	embedded	active	8/16/32 bit processors	[16]
ERIKA Enterprise	GPL+Linking exception	Open Source	embedded	active	ARM7, H8 (Hitachi), Nios2 (Altera), PIC24/dsPIC/PIC32 (Microchip), ST10 (ST Microelectronics)/C167 (Infineon), PPC z7 Mamba, AVR, Tricore1, Mico32, S12XS, H8	[17]
EROS	GPL	open source	experimental research use	dormant	IA32	[18]
Femto OS	GPLv3	open source	embedded	active	AVR	[19]
FreeOSEK	GPLv3	open source	embedded	active	Posix, Windows, ARM7	[20]
FreeRTOS	modified GNU GPL	open source	embedded	active	ARM, AVR, AVR32, Freescale ColdFire, HCS12, IA32, MicroBlaze, MSP430, PIC, Renesas H8/S, 8052, STM32	[21]
FunkOS	modified Sleepycat license	open source	embedded	active	AVR, MSP430, ARM Cortex-M3	[22]
Fusion RTOS	free	?	semi-general purpose	active	ARM, Blackfin, StarCore, DSP 56800E
HeartOS	proprietary	closed	safety critical	active	x86, PowerPC, PowerQUICC	[23]
Helium	free	?	?	?	Open-Source RTOS for HCS08 & AVR MCUs	[24]
HP-1000/RTE	?	?	?	?	?	[25]
INTEGRITY	?	?	?	active	ARM, XScale, Blackfin, Freescale ColdFire, MIPS, PowerPC, x86	[26]
ioRTOS	proprietary	closed	embedded, safety critical	active	TI TMS320 Families (x2812, c6416)	[27]
LynxOS	proprietary	source code available	embedded	active	Motorola 68010, x86/IA-32, ARM, Freescale PowerPC, PowerPC 970, LEON3	[28]
MaRTE OS	GNU GPL	open source	embedded	active	IA-32	[29]
MenuetOS	?	?	?	?	?	[30]
MQX	?	source code available	embedded	active	Freescale ColdFire, List of Freescale products,	[31]
MERT	?	?	?	inactive	PDP-11	?
Multiuser DOS	?	?	?	?	?	?
Nano-RK	mixed	open source	embedded	active	AVR, MSP430	[32]
Neutrino	proprietary	source code provided	microkernel	active	ARM, MIPS, PPC, SH, x86, XScale	[33]
Nokia OS	?	?	embedded GSM devices	?	ARM	?
Nucleus OS	proprietary	source code provided	embedded	active	AMD Au1100, ARM, Atmel AT91 series, Atmel Nios II, Freescale iMX, Freescale MCF, Freescale MPC, Marvell PXA series, MTI, NEC uPD6111x, Sharp LH7 series, ST, TI OMAP, TI TMS320 series, Xilinx Microblaze	[34]
NuttX RTOS	BSD	open source	embedded, small footprint	active	Linux user mode, ARM7, ARM9, 8052, SH-1, Renesas MC16C/26, Zilog Z16F, Zilog eZ80 Acclaim!, Zilog Z8Encore!, Z80, partial ports for MIPS	[35]
On Time RTOS-32	proprietary	source code available	embedded	active	32/64-bit x86	[36]
OS4000	proprietary	closed	process control	maintenance only	GEC 4000 series	?
OpenRTOS	proprietary?	source code available	embedded	active	see FreeRTOS	[37]
OSA	BSD	open source	embedded	active	PIC10-PIC24, AVR 8bit	[38]
OSE	proprietary	closed	general purpose	active	ARM, PowerPC, MIPS, IXP2400, TI OMAP, …	[39]
OS-9	proprietary	available to customers	embedded	active	ARM/strongARM, MIPS, PowerPC, SuperH, x86/Pentium, XSCALE, Motorola 6809, Motorola 68000-series	[40]
OSEK	n/a	specification	embedded	active	engine control units	[41]
Phar Lap ETS	?	?	?	?	?	?
PaulOS	GNU GPL	open source	embedded	?	?	[42]
PICOS18	GNU GPL	open source	embedded	?	PIC18	[43]
Phoenix-RTOS	GNU GPL	open source	embedded	?	ARM7, X86, PowerPC	[44]
PikeOS	proprietary	available to customers	safety critical, virtualization	active	PPC, x86, ARM, MIPS, SPARC/Leon, SuperH	[45]
Portos	proprietary	source code provided	embedded, small footprint	active	DSP/BIOS (ARM soon)	[46]
POK	BSD	open source	embedded	active	x86, PowerPC, SPARC	[47]
PowerTV	proprietary	?	?	?	?	[48]
Prex	BSD	open source	microkernel	active	ARM, IA32	[49]
pSOS	proprietary	?	?	discontinued	Motorola 680x, Motorola 68000	?
QNX	mixed	?	general purpose	active	IA32, MIPS, PowerPC, SH-4, ARM, StrongARM, XScale	[50]
Q-Kernel	proprietary	available to customers	embedded	active	PIC-30, PIC-24, dsPIC, PIC32MX	[51]
RDOS	proprietary	?	general purpose	defunct	Data General Nova, Data General Eclipse	n/a
RMX	?	?	?	active	8080, 8086, 80386 or higher	[52]
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, ARM	[53]
RTEMS	modified GNU GPL	?	embedded	active	ARM, Blackfin, ColdFire, TI C3x/C4x, H8/300, x86, 68k, MIPS, Nios II, PowerPC, SuperH, SPARC, ERC32, LEON, Mongoose-V	[54]
rt-kernel	mixed	available to customers	embedded	active	ARM7, ARM9, ARM Cortex-M3, Blackfin, PowerPC, Windows (simulation)	[55]
RTLinux	GNU GPL	open source	general purpose	active	same as Linux	[56] Real-Time Linux Wiki
RT-Thread	?	open source	?	active	?	[57]
RTXC Quadros	proprietary	source available	embedded	active	ARM - Atmel/Freescale/NXP/ST/TI, Blackfin, Coldfire/68K, PowerPC, StarCore, TI/Luminary Stellaris, TI OMAP, XScale	[58]
Salvo	proprietary	closed	embedded	active	8051, ARM ARM7TDMI and Cortex M3, Atmel AVR and Mega AVR, Epson S1C17, Motorola M68HC11, TI MSP430, PICmicro 12/14000/16/17/18, PIC24, dsPIC, PIC32, TMS320C2000	Salvo - RTOS for tiny places (a Pumpkin Inc. TM)
SCIOPTA	proprietary	closed, source available	embedded, safety related	active	ARM, Cortex-M3, Cortex-M0, XScale, PowerPC, ColdFire, HCS12, M16C, MSP430, Windows(simulation)	[59]
SDPOS	GNU LGPL	open source	embedded	active	ARM, Cortex-M3, Blackfin, PIC18, PIC24, i386 win32/linux synthetic targets	[60]
SHaRK	GNU GPL	open source	?	?	?	[61]
SimpleAVROS	GPLv3	open source	embedded	active, beta	AVR only	n/a
SINTRAN III	?	?	?	?	Norsk Data computers	n/a
Sirius RTOS	proprietary	available under license	embedded	active	x86, i386+, ARM, 68k, 8051, ...	[62]
SMX RTOS	proprietary	available under license	embedded	active	ARM, Cortex, ColdFire, PowerPC, x86, ...	[63]
SOOS Project	free	open source	embedded	active, beta	H8/300	[64]
Symbian OS	Eclipse Public License	open source	embedded	active	ARM	[65]
Talon DSP RTOS	proprietary	?	embedded DSP	active	TMS320	[66]
T-Kernel	free under T-License	source available	embedded RTOS	active	ARM/MIPS/SH/others	[67]
THEOS	?	?	?	?	?	[68]
ThreadX	proprietary	available to customers	?	active	ARC, ARM/Thumb, AVR32, BlackFin, ColdFire/68K, H8/300H, Luminary Micro Stellaris, M-CORE, MicroBlaze, PIC24/dsPIC, PIC32, MIPS, V8xx, Nios II, PowerPC, SH, SHARC, StarCore, STM32, StrongARM, TMS320C54x, TMS320C6x, x86/x386, XScale, Xtensa/Diamond, ZSP	[69]
Trampoline Operating System (OSEK and AUTOSAR)	GNU LGPL	open source	embedded	active	AVR, H8/300H, POSIX, NEC V850e, ARM7, Infineon C166, HCS12 or PowerPC	[70]
TNKernel	BSD	open source	embedded	active	ARM, PIC24/dsPIC, HCS08	[71]
Transaction Processing Facility	proprietary	?	general purpose	active	IBM System/360 derivatives	[72]
TRON Project	Specifications are offered for a series of RTOS specifications (ITRON, micro-ITRON, CTRON, etc.) for free. There are free sample implementations floating, but many commercial implementations are offered and used in products.	mixed	mixed	active	many	Not an implementation, but a specification [73][74] eCoS mentioned in the list above offers the API available in micro ITRON specification v3 produced in TRON Project.
TUD:OS	GNU GPL	open source	?	?	IA-32	[75]
Unison RTOS	Open Source and Commercial	Open Source	MCU, DSC, DSP SoC	active	Pic32, ARM Cortex (TI Stellaris, ST STM32, NXP LM1768), SH2A, SH2AFPU, R32C, MIPS4K, {SHARC, Coldfire, TMS320, Altera NIOS, Xilinx Microblaze, Proprietary}	[76]
µC/OS-II	proprietary	Available under license	embedded	active	ARM7/9/11/Cortex M1/3, AVR, HC11/12/S12, Coldfire, Blackfin, Microblaze, NIOS, 8051, x86, Win32, H8S, M16C, M32C, MIPS, 68000, PIC24/dsPIC33/PIC32, MSP430, PowerPC, SH, StarCore, STM32, …	[77]
µ/OS-III	proprietary	Available under license	embedded	active	ARM7/9/11/Cortex M1/3, AVR, HC11/12/S12, Coldfire, Blackfin, Microblaze, NIOS, 8051, x86, Win32, H8S, M16C, M32C, MIPS, 68000, PIC24/dsPIC33/PIC32, MSP430, PowerPC, SH, StarCore, STM32, …	[78]
UNIX-RTR	?	?	?	?	PDP-11	?
µTasker	proprietary	Open-code. Free for non-commercial or with support license	embedded	active	Coldfire M522XX, AVR32, SAM7X, Luminary Micro, LPC2XXX, STR91X, NE64	[79]
u-velOSity	?	?	microkernel	active	?	[80]
velOSity	?	?	?	active	Power Architecture, ARM/XScale, MIPS, x86/Pentium, ColdFire, Blackfin, OMAP, DaVinci	[81]
VRTX	?	?	?	?	ARM, MIPS, PowerPC, RISC	[82]
VxWorks	proprietary	?	embedded	active	ARM, IA32, MIPS, PowerPC, SH-4, StrongARM, xScale	[83]
Windows CE	proprietary	Microsoft Shared Source	embedded	active	x86, MIPS, ARM, SuperH	[84]
Xenomai	GPLv2	Open Source	general	active	x86, x86_64, PowerPC, ARM, Analog Devices Blackfin BF52x, BF53x, BF54x and BF56x	[85]
xPC Target	proprietary	closed	real-time testing/embedded	active	x86	[86]
MontaVista Linux	?	?	embedded	active	?	[87]
µnOS	?	?	?	historic	Motorola 68k	?

External links

• "How to Choose a Real-Time Operating System" by Michael Barr

• "Linux and POSIX Real-Time Operating System Issues" by Kim Rowe