A realtime kernel lets you focus on your application code, getting to market faster by building on a solid platform. And an RTOS allows you to manage where your code spends it's time so your system runs efficiently, which is critical in power-sensitive IoT applications. There are many RTOSes that run on Tensilica processors and DSPs, see the links or mouse over the tools menu to find your RTOS and how to get it. Other OS kernels are also available, if you don't see the one you need, please tell what you need.
Each Tensilica processor has been optimized by your SoC supplier to meet their design targets, from extreme DSP to lightweight fast control and everything in between. Changing instruction sets can require changes in the OS kernel, but Cadence has developed software technology that allows a single kernel port to run on any Tensilica processor, even one with custom instructions and state. Cadence's XOS kernel is a reference design that shows how to develop a single RTOS kernel that will run on any Tensilica processor configutation.