How secure were these devices? How much work was put onto application developers to maintain isolation? I mean it wasn&#x27;t feasible back then since we didn&#x27;t have MMUs (ifaik)<p>This argument is pretty poor, since we&#x27;ve done a lot of things - cooperative multitasking, windows versions which had little to no isolation between the root user and other users, etc. etc. it doesn&#x27;t mean they are the best approach now, or were even a good idea at the time. Yes we got them to work. Microsoft Bob and Windows ME worked too.<p>I don&#x27;t think the javascript PC emulator runs that acceptably fast either. That was more of a toy example, I don&#x27;t think you&#x27;ll find many people using that for anything real.<p>At the kernel level performance&#x2F;resource usage really does matter. I don&#x27;t know enough about OCaml to comment on how it performs but especially when you make your argument about how (allegedly) terribly linux performs in certain circumstances, and that&#x27;s a lot of what the selling point of unikernels are, it doesn&#x27;t really follow to talk about how &#x27;acceptable&#x27; performance is possible from higher level languages.