← MS OS/2 Patents
The boot screen of Microsoft OS/2 1.3
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.
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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