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From: mark@markshome (mark weiser)
Newsgroups: comp.sys.m68k
Subject: Re: move sr/move ccr: crock
Message-ID: <5158@mimsy.UUCP>
Date: Thu, 22-Jan-87 23:57:45 EST
Article-I.D.: mimsy.5158
Posted: Thu Jan 22 23:57:45 1987
Date-Received: Fri, 23-Jan-87 03:51:03 EST
References: <809@imagen.UUCP>
Sender: news@mimsy.UUCP
Reply-To: mark@markshome.UUCP (mark weiser)
Organization: U of Maryland, Dept. of Computer Science, College Pk., Md. 20742
Lines: 23
Keywords: logic?

In article <809@imagen.UUCP> geof@imagen.UUCP (Geoffrey Cooper) writes:
>In the 68010 and 68020 move from
>SR is a privileged instruction.
>This appears to be a crock.
>My question is why the lords of 68000-land did this?  

Actually, in my opinion, not doing it this way is a crock.  A similar
instruction on the 80386 is NOT privileged, and that means the 80386
cannot be fully virtualized, and that means that no one can be sure of
writing an operating system which will be able to transparently run
80386 binaries, (such as 80386 MS-DOS, should there ever be such a
thing.)  So everyone just has to sit on their hands waiting and hoping
that when Microsoft does release such a thing, it will not use any of
these spoof-proof instructions to see if it being hypervised.

I could speculate that Microsoft, IBM, and Intel conspired to build
the 80386 this way, rather than making it virtualizable, for devious
market control reasons.  But I won't.
-mark

Spoken: Mark Weiser 	ARPA:	mark@mimsy.umd.edu	Phone: +1-301-454-7817
CSNet:	mark@mimsy 	UUCP:	{seismo,allegra}!mimsy!mark
USPS: Computer Science Dept., University of Maryland, College Park, MD 20742