This paper examines different options for putting a real-time operating system (RTOS) on a system on a chip (SOC). There are basically three options: 1) purchase an off-the-shelf RTOS, 2) write your own RTOS, and 3) use a software synthesis tool to automatically generate an RTOS. If you purchase one, what is available and what are the tradeoffs? If you write your own, which issues do you need to take into account? If you synthesize one, what tools are available and how do they work?