Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!uunet!mcsun!ukc!edcastle!erck12
From: erck12@castle.ed.ac.uk (Gnome)
Newsgroups: comp.sys.ibm.pc
Subject: Re: 80286 protected mode, What on earth is a
Keywords: 80286, protected mode
Message-ID: <411@castle.ed.ac.uk>
Date: 14 Sep 89 19:30:03 GMT
References: <1219@marlin.NOSC.MIL>
Reply-To: erck12@castle.ed.ac.uk (Gnome)
Organization: Edinburgh University Computing Service
Lines: 20

In article <1219@marlin.NOSC.MIL> jbjones@marlin.nosc.mil.UUCP (John B. Jones) writes:
-What is protected mode?  Is there an unprotected mode?  It sounds like
-some programming term, but what's it for?
-Thanks in advance for turning some lights on.

	As far as I know (and most of this knowledge is 2nd hand) the 80286 can
operate in two modes, protected and unprotected. The former of these is the real
80286, while the latter, which is used by DOS, makes it act like a 8086/88. The
term protected comes from the protected memory scheme available in that mode.
This is needed by multi-tasking operating systems to stop one process
corrupting anothers memory. OS2 uses protected mode, except when the DOS box is
active. If you think all this is complicated the 80386 has four modes! It has
the two suported by the 80286, true 80386 mode, and multi-8086 mode (which
simulates an individual 8086 in each 1M of the memory map - nice!). I hope the
lights are at least glowing now.
-- 

 Geoff Ballinger,                    JANET: Geoff@Ed.Ac.Uk
 CS/AI,                               ARPA: Geoff%Uk.Ac.Ed@nsfnet-relay.Ac.Uk
 Edinburgh University.                UUCP: ...!uunet!mcvax!ukc!Ed.Ac.Uk!Geoff