MS OS/2 Patents

Microsoft OS/2 1.3 Banner

The boot screen of Microsoft OS/2 1.3

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2 Responses to Microsoft OS/2 1.3 Banner

  1. Is it me, or the faster the computer the longer you get to stare at this notice?

    It’s for switching the 286 from protected mode to real, right?

    It is a very cool hack, and it gave rise to the first big competitor to OS/2… dos extenders.

  2. michaln says:

    I don’t think the notice is intentionally displayed longer on faster computers, but I’m pretty sure MS OS/2 1.3 with LADDR disk drivers takes a lot longer to boot on systems where ATAPI devices are present.

    And no, the patent is not for switching from protected back to real mode on a 286, that was already implemented in the original IBM PC/AT BIOS. The patent covers primarily a dual-mode OS which can execute both in protected and real mode, with emphasis on bi-modal code.

    Some DOS extenders may have technically violated parts of the patent, but not the bulk of it; in DOS extenders, the OS was implemented strictly as 16-bit real mode code, without the elaborate setup needed to run the core of the OS in both real and protected mode.

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