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PostPosted: Sun Feb 19, 2017 7:41 pm 
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That's how I'd understand that language. The 6502's masks were new in 1975-1978, so a derivative work (the 2A03) designed in 1982ish wouldn't be relevant... BUT because the "commercial exploitation" of the NES postdates the mask protection law, it "should" have had mask exclusivity until 1993ish or so.

I am not a lawyer, so take that with an enormous grain of salt.


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PostPosted: Sun Feb 19, 2017 8:45 pm 
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zeroone wrote:
I still don't understand why Commodore didn't sue the hell out of Ricoh and Nintendo

According this "Iwata Asks" interview Ricoh had a license:

Quote:
But Ricoh wanted us to use the 6502, which they had the license for.


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PostPosted: Sun Feb 19, 2017 9:30 pm 
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cyc wrote:
According this "Iwata Asks" interview Ricoh had a license:


Then, that begs the question, why did they have to disable decimal mode?


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PostPosted: Sun Feb 19, 2017 9:32 pm 
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If they did have a license, it might have been for a reduced functionality subset so as not to compete with the first-party 6502.

On the other hand, there's an anecdote in On the Edge that MOS was surprised to discover that the 2A03's CPU core was a 6502 with the patented parts scratched off.


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PostPosted: Mon Feb 20, 2017 11:25 pm 
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Real question i want to know:
"Who first engineered hybrid NTSC/PAL ("Dendy timings") famiclones,
and which CPU and PPU models was really first on this timings..."


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PostPosted: Sat Feb 25, 2017 8:14 am 
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Eugene.S wrote:
Real question i want to know:
"Who first engineered hybrid NTSC/PAL ("Dendy timings") famiclones,
and which CPU and PPU models was really first on this timings..."

Real good question!!

How could they have cloned the chips??
Microfilming/photographing it??
Was this kind of technology available back in the day??
Reverse engeneering?
How would they got the duty cycles wrong on the APU??


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PostPosted: Sun Feb 26, 2017 3:20 am 
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My simple guess is that Chinese engineers made their own CPU and PPU trying to match the original ones by reverse engineering them, but they made mistakes with things like rectangle duty cycle. The chips used in Dendy was made for PAL countries, but they included some characteristics of the NTSC chips to maintain compatibility with NTSC games, as most games in these markets were either bootlegs of licensed Japanese games, or unlicensed Taiwanese originals.


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PostPosted: Sun Feb 26, 2017 9:35 am 
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Would this be cost effective??
How much time a group of experienced engineers could do it back in the day?
Maybe the "plans" (I don't know exactly how to say that) for the chip or part of them have leaked. Who knows??


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PostPosted: Sun Feb 26, 2017 12:49 pm 
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Wouldn't they probably have gotten many more things wrong than just the audio duty cycles if they were doing this through reverse engineering?


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PostPosted: Sun Feb 26, 2017 2:46 pm 
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I'd presume they're using a direct copy of the 6502 mask, so probably the CPU by itself is pretty accurate? (Do famiclones typically have a decimal mode?)

It's plausible that there's lots of inaccuracies with the APU/PPU implementations that just haven't been thoroughly investigated. We've spent a lot of time testing dark areas of the authentic NES, but nowhere close to that attention has been spent on clones. That's a whole lot of leeway to do things differently that wouldn't make a noticeable difference in all existing games, or even just almost all.

E.g. when I started looking closely at the MMC5, I couldn't find any documentation that precisely described how its length counter was different than the 2A03's, or whether any sweep functionality existed, etc. No existing games used it so it didn't matter unless you actually wanted to go looking for it. Almost all emulators don't have a correct implementation of this stuff, but it completely doesn't matter because there's no ROMs that rely on it.


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PostPosted: Sun Feb 26, 2017 3:08 pm 
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Yeah I think they got more things than the duty cycle wrong.
I'm no expert on Famiclonese but I also heard that there are clones with a working decimal mode. There are even clones (by Waixing I think) that only plays its own cartridges, and clones that are more personal computers than game consoles, but are using Famiclone hardware because it's cheap to make and it has tons of compatible games and programs available already.


Fisher wrote:
Would this be cost effective??
How much time a group of experienced engineers could do it back in the day?

Cheaper than designing your own system. Plus it already had games.
China had and still has lots of engineers. There are technical universities founded only for the reason of mass producing more engineers to quickly build things like railroads.

I mean even Japanese Ricoh ripped off the MOS 6502. Unless they really had a legal licence, but I doubt that considering they chopped off the decimal circuitry.


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PostPosted: Sun Feb 26, 2017 3:51 pm 
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Pokun wrote:
Unless [Ricoh] really had a legal licence, but I doubt that considering they chopped off the decimal circuitry.
The decimal circuitry may have been tied to per-unit royalties, while the license may have (foolishly, in hindsight) not considered that Ricoh could have elided the patent-protected portion of the circuitry.


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PostPosted: Sun Feb 26, 2017 4:16 pm 
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What kind of tests should I try?
Maybe I should start with these test ROMs??
I don't promise much, since all I have is a flash ROM and a UxROM socketed board.


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