Re: R6502AP

From: Marko Mäkelä <*msmakela_at_gmail.com*> Date: Thu, 27 Nov 2014 15:52:49 +0200 Message-ID: <20141127135249.GC1821@x60s> · msmakela_at_gmail.com

On Thu, Nov 27, 2014 at 10:56:41AM +0100, Anders Carlsson wrote:
>Groepaz wrote:
>
>>>Does anyone have a NES? Were undocumented opcodes used in any NES games?
>>iirc the flag is ignored... and there are illegal opcodes, but they 
>>dont exactly match the known ones -> 
>>http://en.wikipedia.org/wiki/2A03
>
>See also this page discussing the 6502 decimal mode, which mentions 
>that the 2A03 handles setting and clearing the decimal flag, but 
>doesn't implement the decimal mode. This is achieved by removing five 
>transistors in the core.
>
>http://visual6502.org/wiki/index.php?title=6502DecimalMode

Thanks, this was the missing piece of information.

Isn't it ironic how Nintendo is allowed to copy from others but not vice 
versa? As far as I understand, it is not a copyright violation to copy a 
physical item if some minor details change. It would be legal, provided 
that no patents, design patents or trademarks are violated either.

	Marko

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