Path: utzoo!mnetor!uunet!husc6!think!ames!ucbcad!ucbvax!CORY.BERKELEY.EDU!dillon
From: dillon@CORY.BERKELEY.EDU (Matt Dillon)
Newsgroups: comp.sys.amiga
Subject: Re: Piggyback CPU boards (also legal C expressions)
Message-ID: <8712111630.AA17999@cory.Berkeley.EDU>
Date: 11 Dec 87 16:30:42 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Lines: 22

>I've seen this mentioned a number of times, but no concrete examples of how
>it would be used or cases which would break with a 68020.
>
>Is moving the status register something that would only happen if you used
>assembler, or do any of the compilers generate it in certain cases? I certainly

	I know of no compilers which use MOVE SR, it is strickly a
hand-programmed opcode.  The SR contains the condition codes, supervisor state,
trace mode, and interrupt mask.  The only reason anybody uses MOVE SR,x  is
to check the trace mode, supervisor state, or interrupt mask.  The condition
codes can be read/written with MOVE CCR.  Motorola decided MOVE SR should 
become privilaged (user programs should not know about supervisor flags) under
the 68010 and 68020.

	I see it in copyprotection a lot, but not much else.

>Speaking of things breaking, is a numeric constant of the form 08 or 09
>strictly legal under K&R C? It showed up in an old C-A program compiled under

	Not legal.  It is supposed to be octal.

				-Matt