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Path: utzoo!watmath!watnot!watdragon!jsgray
From: jsgray@watdragon.UUCP (Jan Gray)
Newsgroups: net.micro.amiga
Subject: Re: C Philosophy
Message-ID: <1146@watdragon.UUCP>
Date: Sun, 22-Jun-86 10:54:36 EDT
Article-I.D.: watdrago.1146
Posted: Sun Jun 22 10:54:36 1986
Date-Received: Mon, 23-Jun-86 00:40:55 EDT
References: <8606210754.AA01488@pavepaws>
Reply-To: jsgray@watdragon.UUCP (Jan Gray)
Organization: U of Waterloo, Ontario
Lines: 26
Summary: 

In article <8606210754.AA01488@pavepaws> dillon@PAVEPAWS.BERKELEY.EDU (Matt Dillon) writes:
>>Jeff Gortatowsky       {allegra,seismo}!rochester!kodak!elmgate!jdg
>>
>>Wrong.  Sorry but this is not the case.  The 68000 inside your Amiga is
>>a 16 bit processor that just happens to have 32 bit registers and a 32
>>bit register-to-register data path.  I call your attention to Tables
>>starting on page 187 of the MC68000 Programmer's Reference Manual, 4th edition
>>(C) 1984 Motorola Inc.  These tables clearly show that almost all
>>instuctions pay a penalty for using a long.  ....
>
>Not Wrong, Sorry.  My opinion.  Refering to the same page on the manual,
>I would like to point out that register addressing modes take no longer
>using 32 bits than 16 bits.

Wrong.  Perhaps the *addressing* takes the same time; however the operations
don't.  The 68000 has internal 16 bit ALUs;
	ADD.W	D0,D1	takes 4 cycles
	ADD.L	D0,D1	takes 8 cycles.

C code which assumes 32 bit ints will run significantly slower on a 68000.
The 68020 is another story!

"You'd just watch yourself.  We're wanted men.  I have the death sentence
 on 12 systems!"

Jan Gray    jsgray@watdragon    University of Waterloo    519-885-1211 x3870