Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!utgpu!utcsri!utegc!utai!anton
From: anton@utai.UUCP
Newsgroups: comp.sys.ibm.pc
Subject: Re: Switching from Protected to Real Mode
Message-ID: <4047@utai.UUCP>
Date: Mon, 24-Aug-87 18:59:03 EDT
Article-I.D.: utai.4047
Posted: Mon Aug 24 18:59:03 1987
Date-Received: Tue, 25-Aug-87 04:08:08 EDT
References: <1387@imagen.UUCP>
Reply-To: anton@ai.UUCP (Anton Geshelin)
Organization: CSRI, University of Toronto
Lines: 21
Keywords: 286
Summary: 

In article <1387@imagen.UUCP> geof@imagen.UUCP (Geoffrey Cooper) writes:
>Is there a way (I deduce from recent net messages that there is) for a
>program to switch from 286 protected mode back to real address mode,
>without rebooting the machine?  
>	
>I understand that the only way to tell the '286 to switch is via
>hardware reset.  I think this means that you lose control of the
>processor.  Does MS-DOS have a way to accomodate such a "hot boot"?
>
>Don't RAM disks for the PC-AT have to do this?
>
>- Geof Cooper
>  IMAGEN
>-- 
>{decwrl,sun,saber}!imagen!geof


There is an undocumented instruction in the 286 which will throw you back
into the unprotected mode.  Microsoft has found it so useful that they
insist that Intel not fix it in the 386.  At least, these are the
rumors I heard.