Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!husc6!cmcl2!rutgers!mcnc!ece-csc!ncrcae!ncr-sd!hp-sdd!hplabs!hp-pcd!hpcvlo!john
From: john@hpcvlo.HP.COM (John Eaton)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Switching from Protected to Real Mode
Message-ID: <1610033@hpcvlo.HP.COM>
Date: Wed, 26-Aug-87 13:53:26 EDT
Article-I.D.: hpcvlo.1610033
Posted: Wed Aug 26 13:53:26 1987
Date-Received: Sat, 29-Aug-87 11:55:34 EDT
References: <1387@imagen.UUCP>
Organization: Hewlett-Packard Co., Corvallis, OR, USA
Lines: 19

<<<<
< 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.
----------

They better be insisting that Intel add it to the 286 spec. Until they do
there is no guarentee that it will still be there after the next mask rev
or when any new vendor starts making chips. The I8088 had a undocumented
POP CS instruction that NEC didn't put into the V-20. This caused problems
for some programs that used it.



John Eaton
!hplabs!hp-pcd!john