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From: heiby@mcdchg.UUCP
Newsgroups: comp.sys.m68k
Subject: Re: MC68030 & MC68882 now out and available; comparisons with MC68020?
Message-ID: <2274@mcdchg.UUCP>
Date: Wed, 4-Nov-87 14:59:52 EST
Article-I.D.: mcdchg.2274
Posted: Wed Nov  4 14:59:52 1987
Date-Received: Sat, 7-Nov-87 17:14:40 EST
References: <4733@elroy.Jpl.Nasa.Gov> <542@amc.UUCP> <3570@ccicpg.UUCP>
Reply-To: heiby@mcdchg.UUCP (Ron Heiby)
Organization: Motorola Microcomputer, Schaumburg, IL
Lines: 18

Allen H. Brumm (allen@ccicpg.UUCP) writes:
> >The 68882  *** IS *** a drop in replacement for the 68881.
> 
> This may be true for hardware, but not software.  The internal state frames
> for the idle and busy states on the '882 are larger than that of the '881.

I think that the intention of the statement was that it is a drop-in
replacement in the hardware sense *and* in the USER LEVEL software sense.
If you are mucking around with the internal state frames of a chip in
a way that violates the documented ways of using it, then you get what
you deserve.  In the same sense, the stack frames generated by (for
example) a BUS ERROR with a MC68030 will differ from those generated by
the same condition with a MC68020.  Obey the rules and you won't get burned.
The whole point is that the '030 is USER LEVEL OBJECT CODE COMPATIBLE
with the '020.
-- 
Ron Heiby, heiby@mcdchg.UUCP	Moderator: comp.newprod & comp.unix
"I know engineers.  They love to change things."  McCoy