Not all RTOS are equal. They are designed for different purposes and have different strengths. We have selected three that should cover most needs from small projects to Safety Critical systems. All three have support software and various stacks.
embOS is a priority-controlled real time operating system, designed to be used as foundation for the development of embedded real-time applications. It is a zero interrupt latency, high-performance RTOS that has been optimised for minimum memory consumption in both RAM and ROM, as well as high speed and versatility. > Link to
The SCIOPTA architecture is specifically designed to provide excellent real-time performance and small size. Internal data structures, memory management, interprocess communication and time management are highly optimised. Suitable for SAFETY CRITICAL applications. > Link to
IAR PowerPac is a fully-featured real-time operating system (RTOS) combined with a high performance file system. comes with sample projects and board support packages for ARM devices from different manufacturers. The IAR PowerPac family also includes USB and IAR PowerPac TCP/IP. These products are sold as add-on options to IAR PowerPac for ARM. > Link to
Keil have traditionally produced a basic RTOS for each of their compilers. These are suitable for many applications where basic small and fast systems are required > Link to