Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!uunet!mcsun!sunic!tut!pl
From: pl@etana.tut.fi (Lehtinen Pertti)
Newsgroups: comp.sys.m68k
Subject: Re: 68000 and 68010 questions
Message-ID: <11936@etana.tut.fi>
Date: 23 Mar 90 13:12:18 GMT
References: <8215@cs.utexas.edu>
Sender: News@tut.fi
Lines: 25

From article <8215@cs.utexas.edu>, by rhwang@cs.utexas.edu (Rwo-Hsi Wang):
> 
>     2.  (Question about 68010)  According to the (same) manual, it states
> 	(in appendix F.2, Operand effective address calculation times) that 
> 
> 		Several instructions do not need the operand at an effective
> 	    address to be fetched and thus require fewer clock periods to
> 	    calculate a given effective address than the instructions that
> 	    do fetch the effective address operand.
> 
> 	My questions is: what instructions does the above sentence refer to?
> 	(that is, how do I know whether an instruction need to fetch the
> 	effective address operand?)
> 

	On some instructions (at least CLR) MC68000 fetches destination
	operand from memory, although it is totally replaced by zero.

	These phenomens are removed on MC68010 and thus the comment.

--
pl@tut.fi				! All opinions expressed above are
Pertti Lehtinen				! purely offending and in subject
Tampere University of Technology	! to change without any further
Software Systems Laboratory		! notice