Re: R6502AP

Date: Thu, 27 Nov 2014 10:41:07 +0100
Message-ID: <10988866.JJqhXXFVTG@rakete>
On Thursday 27 November 2014, 10:53:56 Marko Mäkelä <> 
> On Thu, Nov 27, 2014 at 09:11:27AM +0100, Gerrit Heitsch wrote:
> >So far my impression was that all NMOS-6502 behave the same, including
> >the ones from UMC (I have a 1581 with a UM6502A somewhere). The
> >differences started with the CMOS variants.
> I read somewhere that Nintendo used an unauthorized copy of the 6502,
> where the BCD mode was intentionally disabled in order to avoid
> violating the patent that Chuck Peddle got for it.
> I wonder how that was done. Is the D flag still working, but just being
> ignored? 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 ->


boah im ganzen scheiss Internet is nix los, ich such mir bald Freunde wenn das 
so weitergeht!

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Received on 2014-11-27 10:00:03

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