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From: guy@rlgvax.UUCP (Guy Harris)
Newsgroups: net.micro.68k
Subject: Re: bus error, but why?
Message-ID: <390@rlgvax.UUCP>
Date: Sat, 26-Jan-85 01:17:30 EST
Article-I.D.: rlgvax.390
Posted: Sat Jan 26 01:17:30 1985
Date-Received: Mon, 28-Jan-85 07:16:56 EST
References: <363@nbs-amrf.UUCP> <3500006@iuvax.UUCP>
Organization: CCI Office Systems Group, Reston, VA
Lines: 25

> 
> The problem probably is that you are using an assembler for the 68000
> and not the 68010.  Long words need to be long word aligned when using
> the 68010 whereas they need only be word aligned on the 68000.

Huh?  From p. 47 of the M68000 16/32-Bit Microprocessor Programmer's
Reference Manual, fourth edition, which describes the MC68000, MC68008,
and MC68010:

	Address error exceptions occur when the processor attempts
	to access a word or a long word operand or an instruction
	at an odd address.

Nothing about any restriction more stringent than 16-bit word alignment.
(The 68010, like the 68000, is a 16/32 bit chip, not a full 32-bit chip.
It does 16-bit fetches/stores, and manipulates non-address data 16 bits
at a time.)  The 68020 is a 32-bit chip but has no special alignment
requirements.

If the 010 (or 020) required 32-bit alignment of longword quantities, it
would not be compatible with the 000, which would probably not help its
sales at all.

	Guy Harris
	{seismo,ihnp4,allegra}!rlgvax!guy