Path: utzoo!attcan!uunet!husc6!bloom-beacon!tut.cis.ohio-state.edu!mailrus!purdue!decwrl!hplabs!hp-sdd!ucsdhub!jack!elgar!ford
From: ford@elgar.UUCP (Mike "Ford" Ditto)
Newsgroups: comp.sys.m68k
Subject: Re: opcode emulation (Was: Re: 68020 in a *68010* socket?)
Summary: bummer
Message-ID: <188@elgar.UUCP>
Date: 17 Jun 88 04:54:36 GMT
References: <17206@gatech.edu> <10123@mcdchg.UUCP> <17479@glacier.STANFORD. <6443@cup.portal.com>
Reply-To: ford@kenobi.cts.com (Mike "Ford" Ditto)
Organization: Omnicron Data Systems,  Bonita, CA
Lines: 35

In article <6443@cup.portal.com> chrisj@cup.portal.com writes:
>In Message-ID: <182@elgar.UUCP>, ford@elgar.UUCP (Mike "Ford" Ditto) writes:
>
>>Speaking of 68020/881 emulation, has anyone ever implemented a
>>complete 68020-instruction emulation on the 68010?  The reason I ask
>>is that I encountered a surprising inconsistency in the handling of
>>illegal opcodes on the 68010.
>
>As indicated in appendix D, pp D-6,D-7 of the 68020 User's Manual, all
>members of the 68000 family fully decode the opcode word, and generate
>an illegal opcode exception when appropriate.  However, earlier members
>of the family DO NOT necessarily validate the contents of unused fields
>in extension words, especially those required for indexed addressing.

Well, I'm disappointed; shame on Motorola!  But thanks, Chris, for
pointing out the fine print.

					-=] Ford [=-

"Once there were parking lots,		(In Real Life:  Mike Ditto)
now it's a peaceful oasis.		ford@kenobi.cts.com
This was a Pizza Hut,			...!sdcsvax!crash!kenobi!ford
now it's all covered with daisies." -- Talking Heads




At least one of the
programmers of the
news software was a
total idiot at the
time.  I wonder if he
still is?  Look at
all this wasted
space.