Path: utzoo!utgpu!water!watmath!dalcs!garfield!john13
From: john13@garfield.UUCP (John Russell)
Newsgroups: comp.sys.amiga
Subject: Re: Piggyback CPU boards (also legal C expressions)
Message-ID: <4284@garfield.UUCP>
Date: 11 Dec 87 00:32:50 GMT
References: <2118@crash.cts.com> <36064@sun.uucp>
Reply-To: john13@garfield.UUCP (John Russell)
Distribution: na
Organization: Memorial University of Newfoundland, St. John's
Lines: 33

In article <36064@sun.uucp> cmcmanis@sun.UUCP (Chuck McManis) writes:
>In article <2118@crash.cts.com> spierce@pnet01.cts.com (Stuart Pierce) writes:
>>A friend of mine added a 68020/68881 board to his Amiga 500.  All of the games
>>that we tried broke.  
>
>Generally, people who write games have the annoying habit of ignoring all
>the rules in the interest of speed. Invariably this breaks when the user
>upgrades the system. (Which is why the rules are there in the first place).
>What usually gets people is the Move SR, instruction which is privledged
>in the '020. If they had bothered to use the exec GetCC() function 
>it would not be a problem. 

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
wouldn't want statements like "if (x == 0)" to start breaking :-) ! I imagine
someone skilled enough to program a game on the Amiga in assembly who didn't use
GetCC() when appropriate simply had't run into it, tucked away as it is in the 
middle of the other Exec functions.

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
Greenhills C, and Manx complained since it expected numbers starting with 0
to be either hex (0x...) or octal (0...).

John
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