3 ms·

The 286 was a curious little beast. It did have a sort of an MMU, and, according to Wikipedia, The CPU was designed for multi-user systems with multitasking app

• dfox 4y ago
  286 and for that matter even 386 has the segment-based memory protection mechanism that is somewhat reminiscent of Burroughs mainframes, GECOS and maybe AS/400. There are two giant issues with the idea: it does not work that well on 16b word system and it is totally incompatible with what most of existing code written in C expects. So with 386 Intel had combined that mechanism with traditional MMU and somewhat hack-ish method to turn all that of (reportedly because Microsoft wanted that for Windows/386)
• retrac 4y ago
  A few operating systems, mostly UNIX clones, did exist that specifically took advantage of 286 protected mode. The 286 has user and supervisor modes, and could address up to 16 MB of physical memory. In protected mode it still used 8086 style segmented addressing, but the segments were virtual.
  • Eleison23 4y ago
    The bittersweet fact is that when the 80386 came out, OS designers dispensed with segmentation altogether, because it was conceptually so much easier to just flatten out a single vast address space. So despite the fact that i386 was now capable of really useful and intricate segmented memory architecture, it was the unsegmented, flat virtual address space that won the race.