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bloatfish | 1 year ago

So OS/2 exposes VM86 to the user (https://en.wikipedia.org/wiki/Virtual_8086_mode) (as does Windows) but also emulates POST booting behaviour from diskettes?

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MisterTea|1 year ago

I had no idea this was available. Seems like it is also capable of running doom so that means it allows 32 bit mode somehow?

anyfoo|1 year ago

Win95 (and beyond, and somewhat before) DOS boxes also allowed to run DOOM and other protected mode software. But pretty much only if the software was written for "DPMI" ("DOS Protected Mode Interface")[1], which abstracted all of the protected mode "management" stuff away from the software, like switching into protected mode, allocating memory, etc.

If you ran DOOM, you might remember DOS/4GW. That was a so called "DOS extender", and the DPMI "server" when DOOM ran under DOS. When you ran DOOM under Windows, Windows itself became the DPMI server, and DOS/4GW acted as a thinner layer.

Protected mode software written that way did not run as a v86 task anymore, but closer to a regular Win32 task (it was after all real 32bit software).

[1] Or its predecessor VCPI.