Amiga Exec completely spoiled me when it came to elegance of operating systems. Everything I learned about after it was a huge disappointment, including Mach.

Amiga Exec completely spoiled me when it came to elegance of operating systems. Everything I learned about after it was a huge disappointment, including Mach. Particularly because it demystified the OS. Just a bunch of of lists, and due to the OO nature, they were the same kinds of lists. Here's what a node looks like: next, previous, a type, a priority, a name. A task? A node. With a bunch of extra state. An interrupt? A node. With a lot less extra state. A message? A node. With an optional reply port if the message requires a reply. Reply port? Oh, that's just a port. A port? Yeah, a node, a pointer to a task that gets signaled and a list of messages. How do you do I/O? Send special messages to device ports. No "write() system call", it's queues at the lowest levels and at the API layer.