Early Unix switched contexts by writing the current process out to disk, loading the next runnable process, then jumping to it. Besides that overhead being far

Early Unix switched contexts by writing the current process out to disk, loading the next runnable process, then jumping to it. Besides that overhead being far too slow in modern terms it also did not admit threads nor multiple concurrent cores. There was no need to consider atomic operations or even locks to a large degree. Most people wouldn't appreciate minimalism if they had to use such software on a daily basis.