Famicom AV, PAL NES & Dendy chips decapsulation (progress!)

Discuss emulation of the Nintendo Entertainment System and Famicom.

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lidnariq
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Re: Famicom AV, PAL NES & Dendy chips decapsulation (progres

Post by lidnariq » Mon Oct 30, 2017 11:50 pm

I'm having a very hard time finding whether any of these count as both "common" and "high priority". I can only think of things that would be deemed "points of curiosity" for the common ASIC mappers:
* MMC3: As far as we know, the two variants of the MMC3B are identical to the MMC3A and MMC3C — I wouldn't expect to find an interesting difference there. I think the only big question in my mind would be discovering the niggling details of how Nintendo implemented the PPUA12 edge detection.
* Namco's 108/109/118/119 are hopefully not too hard to find? It'd be interesting to figure out what causes the hazard is that Naruko identified when writing to $0000-$1FFF while executing from $8000-$9FFF.
* MMC1: I'd be idly curious to know how they implemented the MMC1 only paying attention to the first write of a RMW instruction.
* VRC2 and/or clones? Could be interesting to see what the SPI microwire interface looks like.

And then there's various rarer parts that have bigger question marks:
* Namco's 163: Could be interesting to see what the wavetable synthesizer DAC and logic look like. If you get a copy of 独眼竜政宗 = Dokuganryuu Masamune there's a bonus chip-on-board (the one immediately above the copper label "60-12") that's doing something Very Weird, not just being a bonus RAM that's used instead of the normal 163 RAM, but seemingly somehow disabling the normal 163 RAM?
* How exactly does RAMBO-1's IRQ work?
* why does Irem's G-101 have so many pins?

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rainwarrior
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Re: Famicom AV, PAL NES & Dendy chips decapsulation (progres

Post by rainwarrior » Mon Oct 30, 2017 11:57 pm

The one I most care about is the VRC7.

Technically one has already been decapped but I'm still waiting for a decoding of the instrument ROM, which I understand requires some sort of chemical staining process to make visible?
https://forums.nesdev.com/viewtopic.php?f=9&t=12260

lidnariq
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Re: Famicom AV, PAL NES & Dendy chips decapsulation (progres

Post by lidnariq » Mon Nov 13, 2017 7:26 am

Oh, another random one:

Taito's X1-017 (i.e. mapper 82) is connected to the NES's /IRQ line, but no game uses IRQs. It'd be idly interesting to see if (and how) the IRQ hardware is broken, or how one could be triggered.

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Eugene.S
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Re: Famicom AV, PAL NES & Dendy chips decapsulation

Post by Eugene.S » Fri Dec 01, 2017 1:53 pm

I've purchased Madara (VRC6b) and Lagrange Point (VRC7) from ebay.
So, i need to buy PAL NES CPU (RP2A07) and FDS (RP2C33)
for help this project: https://www.qmtpro.com/~nes/chipimages/

VEG
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Re: Famicom AV, PAL NES & Dendy chips decapsulation (progres

Post by VEG » Tue Jul 31, 2018 5:00 am

It would be nice to look at UM6561 also. I know that some people don't like these NES-on-a-chip, but actually it is just further development of UA6527 and UA6538. For example, it is interesting how switching between PAL and NTSC is done in these chips.

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Eugene.S
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Re: Famicom AV, PAL NES & Dendy chips decapsulation (progres

Post by Eugene.S » Wed Aug 01, 2018 4:25 am

I agree, but we still wait man who does decapsulation work

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