Comparison of real-time operating systems

This list of Real-time operating systems enumerates 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	Target usage	Status	Platforms	Official site
ChibiOS/RT	GPL open source	general purpose	active	IA32, ARM, Atmel	[1]
eCos	GPL open source	general purpose	active	ARM, H8, IA32, 68000, MIPS, V8xx, SPARC, etc.	[2]
FreeRTOS	modified GPL	embedded	active	ARM, AVR, AVR32, HCS12, IA32, MicroBlaze, MSP430, PIC, Renesas H8/S, 8052	[3]
Fusion RTOS	free	semi-general purpose	active	ARM, Blackfin, StarCore, DSP 56800E	[4]
Nucleus RTOS	proprietary	embedded	active	?	[5]
Open AT OS	?	embedded GSM devices	?	?	[6]
OSE	?	?	?	ARM, PowerPC, MIPS, IXP2400, TI OMAP	[7]
OSEK	?	?	?	?	?
QNX	mixed	general purpose	active	IA32, MIPS, PowerPC, SH-4, ARM, StrongARM, XScale	[8]
RT-11	proprietary	general purpose	defunct	PDP-11	n/a
RTEMS	modified GPL	embedded	active	ARM, Blackfin, ColdFire, TI C3x/C4x, H8/300, x86, 68k, MIPS, Nios II, PowerPC, SuperH, SPARC, ERC32, LEON, Mongoose-V	[9]
RTLinux	GNU	general purpose	active	same as Linux	[10]
Talon DSP RTOS	proprietary	embedded DSP	active	TMS320	[11]
ThreadX	proprietary	?	active	?	[12]
Transaction Processing Facility	proprietary	general purpose	active	System/360 derivatives	[13]
VxWorks	proprietary	general purpose	active	ARM, IA32, MIPS, PowerPC, SH-4, StrongARM, xScale	[14]
μC/OS-II	proprietary	embedded	active	(many)	[15]