Hi Everyone, I'm not a terribly technical person, but would anyone know what mapper chips are generally used in Famicom Pirate cartridges? I ask because there is a project called PlayPower.org which consists of a community which is trying to design educational software for people in low income countries who's only connection to a computer would be a Chinese $10 Famicom Edutainment system. Do most multi-carts include a general all-purpose mapper chip which can be configured, or just a simple one which works with only early generation titles? In addition, are these chips discrete usually, or is everything just in an epoxy glob these days? Would there be any kinds of low cost Chips that would substitute for a mapper should it be necessary? Any help would be appreciated! @kyuusaku: If your taking a nap and need some random subject to dream about, perhaps you could throw a bit of your sleep-talking my way (^_^);
Hrm... Well the Game Doctors support CNROM, GNROM and U(N/O)ROM styles of bankswitching. If that's any indication of mapper support, I suppose most mappers before 1988 would commonly be supported in other pirates. Especially those 1-in-1000000000000+ cartridges which are filled to the rafters with first generation games, and about a gazillion hacks of them.
Most are glops. There are simpler mappers and there are more complex mappers but because there is no central regulation, you're not going to run into a supplier without finding someone who still makes games. But even Nintendo released mappers that were discrete logic chips. I have one older famicom pirate that has over 10 discrete logic chips making up its "mapper".
Which mappers would be the most universal to develop for? That is, ensuring that when it comes time to manufacture, it is the most likely to be supported, or easy to get support for?
What exactly is needed? I mean it would seem to me something so basic would probably work with something like UNROM/UOROM which is made up of a few basic 74 series chips. It allows for one fixed 16KByte PRG Bank, and up to a total of 256Kbyte (UNROM) or 512Kbyte (UOROM). It's possible with some other chips to add support for WorkRAM at $6000 - $7FFF like MMC1 and other mappers which often save data or just need more RAM have it. I don't think anyone makes mapper chips anymore. If they do you'd have to ask what they can do. There have been many pirate mappers, including MMC3 clones.
MMC1 and MMC3 are by far the most common mappers on NES games. For Famicon things get a bit more confusing as a lot of games that were released using MMC3 or other Nintendo chips in the US used own maker designs, like Konami VRC series, for example. Edit: By this I mean that you will find plenty of MMC1 and MMC3 donor carts.
How difficult would it be to implement MMC1 or MMC3 with off the shelf parts? Is it easy enough to do, or are some parts getting harder to source? Sorry for all the questions. I'm rather a laymen when it comes to hardware! (^_^);
MMC1 would be 20+ off the shelf parts! XD MMC3 around the same actually, benefiting from less random logic and more register files. You can actually make a Sunsoft FME-7 with <15 chips because it fits really well into discrete chips and is still more powerful than MMC3.
You can get mmc1 clone repro boards here for $9: http://www.retrousb.com/product_info.php?cPath=24&products_id=43
The FME7 is an excellent mapper due to its simple design yet powerful features. The only possible complicated part would be the IRQ operation which is CPU based rather than PPU based. Calpis, did you ever complex the schematic for the full FME7 discrete logic board? I remember you were working on it and I think you may have posted a cut down version at some point.
Now I am curious. Is there anywhere such reverse-engineering schematics were documented ? Few years ago I actually took the 315-5235 software specifications and built an clone: I know, looks NASTY but it works. And the way I made it, it connects to the expansion slot on the back of the unit, instead of the cartridge slot. If no cartridge or SEGA card is inserted on the system it boots the ROM on the socket.
FME7's IRQ counter actually really really easy, it's just 4x 74191 and a couple register bits for control. I don't remember, did I post anything? I did a search through my files and did find a schematic (feb of 2009) made up of ~16 chips. I think the only thing missing is WRAM mapping, it's kinda big so I don't feel like piecing together screenshots to upload XD. I really don't suggest anyone try building a discrete FME-7 though, it's a total waste of rare and expensive chips.
damn impressive. How come you're not loaded with cash from inventing/designing something mate? :shrug:
Oh, actually I was talking about the software side of using IRQ. I suppose if the discrete version would be wasteful of chips, the thing to do would be to make it easy to put a FME7 on a CPLD or something. Or help to get BunnyBoy to make a FME7 PCB.
It takes more than ideas and designs heh, takes execution which I'm lacking in and then there's all the competition. Bunnyboy already designed FME7 for the PowerPak, surely he could do a CPLD version if he wanted (if someone were going to publish through him). Really these mappers aren't so hard to design thanks to all the reverse engineering by Kevtris and friends. Besides, building seems a little beyond standard hobbyist level, if one can build (w/o a kit), I think they can design/implement.
I thought about that after I posted. I guess if someone came up with an original game that needed MMC3 or FME7 and wanted BunnyBoy to help them bring it to market, that he probably would be able to get it produced.
