Path: utzoo!attcan!uunet!mcrware!kim
From: kim@mcrware.UUCP (Kim Kempf)
Newsgroups: comp.sys.m68k
Subject: Re: opcode emulation (Was: Re: 68020 in a *68010* socket?)
Message-ID: <708@mcrware.UUCP>
Date: 13 Jun 88 03:11:00 GMT
References: <17206@gatech.edu> <10123@mcdchg.UUCP> <17479@glacier.STANFORD.EDU> <182@elgar.UUCP>
Organization: Microware Systems Corp., Des Moines, Ia.
Lines: 13

In article <182@elgar.UUCP>, ford@elgar.UUCP (Mike "Ford" Ditto) writes:
> Does anyone know whether the 68010 is consistent in reporting illegal
> instructions?  If not, it would seem difficult to emulate the 020
> instruction set (having to check bus errors for illegal addressing
> modes would be pretty bogus).
> 
The 68020 manual from Motorola points out the fact that while the 68010
does indeed fully decode all 65536 possible opcodes, it does not fully
decode the addressing mode modifier word.  They give numerous examples
of how a 68010 can totally botch 68020 instructions until it runs
an illegal opcode.
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Kim Kempf, Microware Systems Corporation	...!sun!mcrware!kim