The Computers: Software: Operating Systems: Realtime: (QNX Realtime )

QNX: leading true realtime OS for PCs, now multiplatform. Small, fast, scalable, fault tolerant, POSIX compliant, preemptive multitasking, runtime memory protection, free downloads, more. Standard APIs and tools (POSIX, Linux, GNU, etc.) are familiar to tens of thousands of developers. Open architecture; available source; Linux and Unix compatible. QNX Realtime Operating Systems Software Computers.

As a microkernel -based OS, QNX is based on the idea of running most of the operating system kernel in the form of a number of small tasks, known as servers. (wikipedia)