Microkernel

Microkernels run most of the traditional kernel functions outside in user mode services. Only the most basic functions like device control and some security and memory handling is performed in kernel mode. This make is easy to change e.g. to a different file management implementation by starting a new service. Drivers can run mostly in user space. Interrupts still need to be handled by the kernel but from on the handling of the interrupt happens in a user mode driver process.

Fast interprocess communication is key in such a concept. Minnix3 features a rendezvous based mechanism with minimum buffering and synchronization overhead.

Microkernals also follow the principle of communicating sequential processes nicely providing a high degree of parallelism with a maximum of isolation.