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- Newsgroups: comp.os.msdos.programmer
- Path: sparky!uunet!mcsun!sunic!ugle.unit.no!alkymi.unit.no!robert
- From: robert@alkymi.unit.no (Robert Schmidt)
- Subject: Re: MS-DOS in 386 protected mode
- Message-ID: <1992Nov19.170201.18621@ugle.unit.no>
- Sender: news@ugle.unit.no (NetNews Administrator)
- Organization: Norwegian Institute of Technology
- References: <37619@uflorida.cis.ufl.edu>
- Date: Thu, 19 Nov 92 17:02:01 GMT
- Lines: 23
-
- In article <37619@uflorida.cis.ufl.edu>, ggh@reef.cis.ufl.edu (Greg Huey - Aymer deGregory) writes:
- >
- > Im trying to write a 'bare-bones' multi-processing os for the 386.
- > I dont wont to create my own dos, obviously I want to use MS-DOS...
- > Question is, how do I do this in protected mode?
- > Presumably, I create the GDT, LDTs, TSSs, IDTs, and the viarious gates...
- > But no matter HOW I map virtual memory with the GDT, LDTs, I cannot make
- > the virtual memory transparent, due to the priv bits and table indicator
- > bit. I need to put the 386 in protected mode, but it has to look the
- > same to MS-DOS, otherwise MS-DOS will fail, wont it? For instance, MS-DOS
- > knows one of its buffer is at seg:offs -- when I put the 386 into protected
- > mode, seg, rather than being a simple address, will now be treated as a
- > selection index into the GDT or LDT.
-
- As I understand it, V806 mode was created just to enable running DOS
- apps (really 8086 apps) while a supervisor protected mode program
- watches everything.
-
- I you try to run DOS in true protected mode, I think you're out of luck.
- Notice that all major task-switching or multitasking systems do the same:
- they put each DOS session in a separate V8086 session.
-
- robert
-
