Depends how "hard" realtime we're talking. For tighter deadlines you'd usually use QNX or PikeOS or the like. The bigger issue is that for higher task frequenci

Depends how "hard" realtime we're talking. For tighter deadlines you'd usually use QNX or PikeOS or the like. The bigger issue is that for higher task frequencies you probably don't want to use big microprocessors, but microcontrollers that don't have a MMU but a MPU max. That rules out Linux quite often (plus space constraints).