Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!mcsun!unido!fauern!faui43.informatik.uni-erlangen.de!csbrod
From: csbrod@informatik.uni-erlangen.de (Claus Brod (turo))
Newsgroups: comp.sys.atari.st.tech
Subject: Re: Instruction timings ?
Message-ID: <1991Jan12.094246.27967@informatik.uni-erlangen.de>
Date: 12 Jan 91 09:42:46 GMT
References: <18805@shlump.nac.dec.com> <27994@cs.yale.edu>
Organization: University of Erlangen, Germany
Lines: 23

fischer-michael@cs.yale.edu (Michael Fischer) writes:

>>I wonder if anyone has a listing of 68000 instruction timings for the ST
>>? I've got a couple of books on ST internals and 68000 programming but
>>neither of them mention instruction speeds at all. I'm trying to write
>>some code to remove all the borders so I need to know exactly how many
>>clock cycles each instruction takes in my code...

Be sure to include in your calculations that, on the ST, some instructions
may take longer than what Motorola tells you. This is due to the fact
that there are some 6-cycle instructions, and the ST bus is shared between
processor and shifter on a 4-cycle-basis. Thus, these instructions can
effectively take 8 cycles instead of 6!

(This applies to any instruction which has an instruction time which
is not a multiple of 4.)


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Claus Brod, Am Felsenkeller 2,			Things. Take. Time.
D-8772 Marktheidenfeld, West Germany		(Piet Hein)
csbrod@medusa.informatik.uni-erlangen.de
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