Just random RT OS's? It's been awhile since I've worked on tiny 8 bit mcus, but all the stuff was really small and seemingly hand rolled, nothing as monolithic as Linux.
I would not be surprised to learn that it varies from company to company and chip to chip, with various bits being shared for common logic.
I would not be surprised to learn that it varies from company to company and chip to chip, with various bits being shared for common logic.