Yeah, most of them did; especially most of the holdovers from the 80s. This was one of the big draws to pulling down "mainframe/workstation" systems like unix

Yeah, most of them did; especially most of the holdovers from the 80s. This was one of the big draws to pulling down "mainframe/workstation" systems like unix (or what MS did by hiring what IIRC was the VMS team to build NT) onto desktop machines. These mainframe systems actually had memory protection, and more generally, had been built to do what "pc OSes" hadn't been designed to do, which was running several programs at once, for long periods of time, and juggling resource contention between them. DOS machines, CP/M machines, Apples, Macs, Commodores, and several other early machines were pretty tactfully designed to avoid the (too heavy for their hardware) complexity of that by simply building themselves to run only one program at a time. There were hacks to let you run multiple programs (like the Multifinder in MacOS 6, which got mainlined into being a permanent thing in 7), but they were just that — hacks. They were fragile. As computers started taking on the burden of juggling tons of different simultaneous programs, this fragility really started to blow up on them, and these previously "seeming stable" systems started to crash all the time.