Modern Mapper Replacement Chips?

Discuss hardware-related topics, such as development cartridges, CopyNES, PowerPak, EPROMs, or whatever.

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Mikey
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Re: Modern Mapper Replacement Chips?

Post by Mikey »

Joe wrote: Wed Jan 11, 2023 12:52 pm If you have more than one bank register, you need to select which one of those registers will drive the ROM's upper address lines according to the cartridge bus upper address lines, and those ROM address lines have to be driven quickly enough for the ROM to produce the correct data within the time limit.
That's a great point. -- I wasn't consdiering the ramifications of multiple bank switching registers...

I guess it could still work with some extra glue logic in a GAL (i.e. address lines and mcu bank control lines go into the GAL, and the high address lines come out), but I really hate it...
lidnariq wrote: Wed Jan 11, 2023 12:55 pmwait, why bother with 8x8 attributes when we can have 8x1
I was wondering if anyone would do that. Neat that someone is working on it! -- I saw that the NES re-reads the palette info each scanline.
lidnariq wrote: Wed Jan 11, 2023 12:55 pmInstead, the win with 8x8 attributes is getting rid of the awful layout of the attribute table.
For me it was about getting more colors into the same 16x16 block. -- I find it really limiting, and I saw that Nintendo made a chip that "fixes" it, so I wanted to use it. -- But yuck, this is just getting really muddy.

To check my understanding the 16x1 could be accomplished by just bank switching on every hblank, right? -- and for 8x1 it would have to bank switch after every palette read (outside of vblank), right?

How hard is it to get a custom mapper accepted by the emulation community? -- Like if someone puts a custom mapper chip in their game that doesn't exist anywhere, can they just share it with the emulator authors? -- Or what is the best way?
lidnariq wrote: Wed Jan 11, 2023 12:55 pmThat's not challenging at all, but it's also not particularly versatile.
I don't follow why, for example, it couldn't accomplish everything the MMC3 does (aside from multiple bank switching registers without some extra glue logic, as Joe points out)?

I would have to look a the other m19 and m69 though to understand where the shortcomings are; I think you could build something really neat out of that layout. But there's probably some other dragon in the details that I haven't spotted yet.
Last edited by Mikey on Wed Jan 11, 2023 2:34 pm, edited 1 time in total.
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rainwarrior
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Re: Modern Mapper Replacement Chips?

Post by rainwarrior »

Mikey wrote: Wed Jan 11, 2023 2:19 pmHow hard is it to get a custom mapper accepted by the emulation community? -- Like if someone puts a custom mapper chip in their game that doesn't exist anywhere, can they just share it with the emulator authors? -- Or what is the best way?
Make a game with it that's worth playing, and it'll get emulated. Otherwise, probably an uphill battle to get anyone to care about it... we've got years and years of fantasy mapper backlog in this place.

Though, making a good game is hard, IMO, so maybe the answer is "pretty hard".
Mikey
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Re: Modern Mapper Replacement Chips?

Post by Mikey »

rainwarrior wrote: Wed Jan 11, 2023 2:26 pm Make a game with it that's worth playing, and it'll get emulated. Otherwise, probably an uphill battle to get anyone to care about it... we've got years and years of fantasy mapper backlog in this place.

Though, making a good game is hard, IMO, so maybe the answer is "pretty hard".
I like it. :)
lidnariq
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Re: Modern Mapper Replacement Chips?

Post by lidnariq »

Mikey wrote: Wed Jan 11, 2023 2:19 pm To check my understanding the 16x1 could be accomplished by just bank switching on every hblank, right? -- and for 8x1 it would have to bank switch after every palette read (outside of vblank), right?
16x1 could indeed be done by the CPU just by switching bankswitched attributes every scanline, and I made a demo many years ago of mapper 19 doing this. (It's not a compelling visualization because I didn't have any good quantization tool at the time)
I don't follow why, for example, it couldn't accomplish everything the MMC3 does (aside from multiple bank switching registers without some extra glue logic, as Joe points out)?
I mean, multiple banks is useful. If it weren't there wouldn't be so many mappers that provide them.

There are three separate independent things that can want to fetch data at the same time from PRG ROM: the main thread, the IRQ and NMI vectors, and prerecorded audio. It's nice to have three independent banks for this – otherwise you have to compromise and choose certain things to glue into the same bank.
I would have to look a the other m19 and m69 though to understand where the shortcomings are; I think you could build something really neat out of that layout. But there's probably some other dragon in the details that I haven't spotted yet.
To be clear, there were lots of games that accepted the limitations and just worked within them. Maybe they didn't use much prerecorded audio, or were structured as a bunch of almost-independent 32KB games (such as one for each level).
calima
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Re: Modern Mapper Replacement Chips?

Post by calima »

It's clear you want to play with hw, but from a sw perspective, if you want useful 8x8 attributes and other features, you're picking the wrong console. Target SNES or Genesis instead.
Mikey
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Re: Modern Mapper Replacement Chips?

Post by Mikey »

I mean, multiple banks is useful. If it weren't there wouldn't be so many mappers that provide them.
I agree -- I just forgot about it when I was hatching up that idea. :lol: -- Again glue logic could work to extend the design further and leave the MCU available to do more in it's "off time" but... that's kind of a crappy (and expensive) mapper solution IMO. -- Not really worth it.

I think you're right, the Romulator with CHR RAM seems like a much more versitle solution than what I was cooking up in my head. :beer:
I made a demo many years ago of mapper 19 doing this.
NEAT. Thanks for sharing that.

This does indeed seem like a pretty cool mapper -- does it have the ability to IRQ on a scanline like MMC3 does?

Also... I'm guessing there's no new source of these Namco mapper chips; otherwise you would have said so before...? -- So if I wanted to use one, I'd have to go the Romulator route...?
It's clear you want to play with hw, but from a sw perspective, if you want useful 8x8 attributes and other features, you're picking the wrong console. Target SNES or Genesis instead.
I'm actually a software guy -- and I am planning to do something for most of my consoles eventually. -- To be clear, I'm not trying to avoid the challenge of the NES by chosing some crazy over powered mapper that turns the NES into a Pentium III with a Voodoo card or something... -- I'm just trying to come to some conclusions on which (mostly period correct) mapper makes the most sense for me to target.

When I started this thread, I was heavily leaning towards the MMC5, but you guys have me pretty convinced that MMC3 is probably the better way to go for general projects -- aside from it being a common chip used in a lot of games, there are modern ASIC replacements available... -- and the scanline IRQ is at least a pretty useful feature. :)
lidnariq
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Re: Modern Mapper Replacement Chips?

Post by lidnariq »

Mikey wrote: Thu Jan 12, 2023 7:48 pm [Namco 163] does indeed seem like a pretty cool mapper -- does it have the ability to IRQ on a scanline like MMC3 does?
... yes? Sort of?

For good and ill, it has a cycle-timed IRQ instead of a PPU-timed IRQ. This means that it works fine even when rendering is disabled, but on the other hand its specific design is bad for repeated IRQs within a frame - each successive IRQ adds a little drift depending on that interrupt's (unknowable, random as a function of what instruction the IRQ was asserted during) latency.

(Not all cycle-timed IRQs have this flaw! VRC4/6/7 (mappers 21/23/24/25/26/85) have a prescaler that means that the IRQ doesn't have to to drift as a function of when the next period is provided. And FME-7 (mapper 69) doesn't stop counting when IRQ is asserted, so you can use the lower byte as a prescaler to get no drift - as long as you want all the IRQs to be spaced by any multiple of 256 cycles)
Also... I'm guessing there's no new source of these Namco mapper chips; otherwise you would have said so before...? -- So if I wanted to use one, I'd have to go the Romulator route...?
If you want your mapper to provide multiple banks for both PRG and CHR, you'll probably just have to use an FPGA - timing is too onerous otherwise. ROMulators are basically out-of-scope for multiple uncorrelated inputs, like the NES's CPU and PPU.
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Re: Modern Mapper Replacement Chips?

Post by Drag »

Fun fact, since all North American cartridges needed to be manufactured by Nintendo, they were all restricted to standard Nintendo mappers and boards (like the MMC1, MMC3, uxrom, axrom, etc). This wasn't the case in Japan (and I'm not sure about the PAL regions).

Therefore, all of the fancy developer-specific mappers are Famicom-only, and the games needed to be converted to a Nintendo mapper for the NA release.

(I don't remember where I originally heard this, so correct me if this is wrong)
Pokun
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Re: Modern Mapper Replacement Chips?

Post by Pokun »

AFAIK, PAL NES cartridges were also all made in Japan by Nintendo, so I'm pretty sure they were limited to the same mappers as NTSC NES carts.
PAL releases were also typically based on NA releases (same translations etc), even if the NA version didn't always actually release (like with Mr Gimmick).

The mapper restriction took place in Japan as well, but a number of companies that had already established a name as a 3rd-party developer seemed to get to keep their permission to produce their own cartridges even after Nintendo came up with that rule, which would explain why there are so many different cartridge designs and colors for Famicom carts (besides mappers).
Compare with all later Nintendo systems, Game Boy, SNES, Virtual Boy, GBC, Nintendo 64, GBA etc where the cartridges almost always were uniform, typically grey and very seldom used mappers outside the handful of mappers Nintendo provided.
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rainwarrior
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Re: Modern Mapper Replacement Chips?

Post by rainwarrior »

Pokun wrote: Fri Jan 13, 2023 12:12 pmThe mapper restriction took place in Japan as well, but a number of companies that had already established a name as a 3rd-party developer seemed to get to keep their permission to produce their own cartridges even after Nintendo came up with that rule, which would explain why there are so many different cartridge designs and colors for Famicom carts (besides mappers).
With the Famicom having no lockout chip, they couldn't physically stop anyone from making their own carts.

I don't think there was a really a restriction in Japan. Some companies worked with Nintendo directly and agreed to have Nintendo make the boards, but to the extent this happened it was more of a mutual business agreement. Nintendo had some leverage there, but nowhere near the same degree as other regions where the lockout made it much harder.

Even in USA officially licensed releases where they had much more control, Nintendo still occasionally permitted publishers to use their own boards or mappers (e.g. Acclaim, Sunsoft). Unlicensed carts were present, but more marginal, unlike Japan where it was the largest portion of the library, I think? Even after Atari/Tengen lost that lawsuit for trying to clone the lockout chip, they still did business together and Nintendo made their boards after that.

Between the lockout chip idea, and Nintendo's huge growth through the Famicom, all subsequent consoles from them have allowed Nintendo a lot more control over releases like that. Still, it strengthens and weakens over time with their market power (e.g. look at the way the Wii U online store got flooded with shovelware as Nintendo struggled to attract higher quality publications).
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Individualised
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Re: Modern Mapper Replacement Chips?

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rainwarrior wrote: Fri Jan 13, 2023 2:19 pme.g. look at the way the Wii U online store got flooded with shovelware as Nintendo struggled to attract higher quality publications).
The 3DS and Switch stores are the same to be fair. Xbox and PlayStation as well - hell, I've even seen straight up bootleg Pokemon and Mario games on the Xbox store, though they would get swiftly taken down. I think it was more to do with shovelware developers cutting costs by no longer releasing physical copies and flooding digital mediums instead. You'll never find physical copies of game show adaptations or Wii Sports knockoffs on current generation platforms.
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Re: Modern Mapper Replacement Chips?

Post by rainwarrior »

All of the platforms have become more permissive since digital distribution, some more than others. XBox in particular allowed free self publishing. I was more just thinking about how Nintendo's particular forms of platform control have mutated over time.

Wii U had basically first party stuff, and then shovelware on there, with almost no in-between. Part of the problem with the Wii U is that after the success of the Wii they adjusted their licensing deals in a way that was unfavourable to third party publishers. For that and other reasons, the platform didn't sell so well, and good quality third-party stuff was driven off, and what we were left with is mostly extremely poor.

With the switch, they're having more success. Part of it is better publishing deals... but at the same time their success has enabled them to be more exclusive about what gets on the switch. It was easier to get terrible software on the Wii U, because they were desperate. The switch has shovelware, too, all the platforms do, but they can afford to reject a lot more of the low end of stuff, and it's not as visible either with so much stuff of better quality on the store to look at instead.
Pokun
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Re: Modern Mapper Replacement Chips?

Post by Pokun »

I remember checking the form for applying as a developer for the Switch when it was still very new, and it seemed to me that it was a much easier process than earlier Nintendo systems (except maybe the Wii U). This was before anyone knew if the Switch were going to be a success or another Wii U and Nintendo probably needed as much 3rd party support as they could get. Later, when success was a fact, they supposedly removed this portal to make applying a bit harder and filter out the least serious developers.

But yeah I think Nintendo's attitude has changed a lot considering how much shovelware there is for the DS and later Nintendo systems. When the Famicom was released they wanted to make ALL games themselves (according to the late Masayuki Uemura this was one reason they choose the 6502 CPU which was still quite unknown in Japan and would prevent most 3rd-party from programming it) because they were afraid the American Atari crash would repeat in Japan. Yamauchi knew they could deliver because they had been very successful with arcade games (both electromechanical and video games) and home pong clones. They loosened this up as Famicom became so successful but I think they have always been quite strict on 3rd-party to ensure quality until more recent years. I guess realizing that they could make a lot of money on their monopolized cartridge production alone also helped (until optical media became the new norm at least).

rainwarrior wrote: Fri Jan 13, 2023 2:19 pm Even in USA officially licensed releases where they had much more control, Nintendo still occasionally permitted publishers to use their own boards or mappers (e.g. Acclaim, Sunsoft). Unlicensed carts were present, but more marginal, unlike Japan where it was the largest portion of the library, I think?
The Famicom and NES both got lots of 3rd party games in all regions AFAIK (Capcom, Konami and Sunsoft were all big), but of course Japan has the biggest library meaning that Famicom has got to have more 3rd party than any other region. I guess that for many smaller makers, releasing a game outside of Japan isn't worth the risk unless the genre is proven to work in the target region. Especially considering you need to pay for localization (even if the game has no text the box and manual got to be translated), specialized cartridge production and Nintendo's license fees.
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