Street Fighter III (3) reproduction? It's possible?

Street Fighter III (3) reproduction? It's possible?
by Harry Hardon on 2007-11-12 (#28170)

Hello, I'm again.

I think this is the best fighting game made for the Nintendo 8-bits.
And, I already have a copy of the game, that I bought back em 1993/1994 or so (yes, I'm from Brazil, all those fantastic pirate games was like water in the ocean here, at time =).

The game "specs" is almost bizarre. Uses mapper 91, but has 128k of PRG (8x16) and 512k of CHR (64x8).

My question is: there's any board that can accept this game? The only way to put it in a cartridge is making a custom board?

I haven't found anything related on the forums, so, sorry if it was discussed before.

Thanks.

Here's a pic:

by tepples on 2007-11-12 (#28172)

Most docs that Google could dig up refer to mapper 91 as the "HK-SF3 mapper", meaning this so-called "Street Fighter III" might have been the most common game on this mapper.

But why is it called SF3 when it's not based on SF3? Is falsifying the sequel number a typical convention of HKO developers?

by 17daysolderthannes on 2007-11-13 (#28253)

tepples wrote:
But why is it called SF3 when it's not based on SF3? Is falsifying the sequel number a typical convention of HKO developers?

that happened all the time with pirate games. Look at Mario 4,5,6,7 etc. etc., some of them are hacks of other games and others are Mario 3, its mostly just to not have the exact title of the real game to give just a smidge less copyright infringement.

by Bregalad on 2007-11-14 (#28266)

You will need to know how it's mapper works and mapper-hack the game (it's a pirate anyways !) to run it on another more common mapper.

by tepples on 2007-11-14 (#28271)

Is there a document about this mapper? Or are other emulators the only document?

by dvdmth on 2007-11-14 (#28280)

The biggest problem is the CHR size (512KB). The only Nintendo-made mapper that supports this much CHR is mapper 5 (MMC5, E*ROM boards). A glance at Nestopia's mapper 91 implementation shows that the game will need IRQ's, 8K PRG switching, and 2K CHR switching (all of which are supported by the MMC5). Unfortunately, not many games were released with the MMC5, so I'm not sure it's feasible to make a repro of this one.

Re: Street Fighter III (3) reproduction? It's possible?
by ramiq27 on 2016-01-06 (#162002)

dvdmth wrote:
The biggest problem is the CHR size (512KB). The only Nintendo-made mapper that supports this much CHR is mapper 5 (MMC5, E*ROM boards). A glance at Nestopia's mapper 91 implementation shows that the game will need IRQ's, 8K PRG switching, and 2K CHR switching (all of which are supported by the MMC5). Unfortunately, not many games were released with the MMC5, so I'm not sure it's feasible to make a repro of this one.

Apologies for necro-bumping the hell out of this thread

Didn't want to start up another one.

I am trying to reproduce this game for the Famicom and was wondering if it's possible to do so based on what you're saying. I hope you're still on this forum.

Is it the same process as reproducing a T*ROM game?
Do I need to rewire some connections?

Re: Street Fighter III (3) reproduction? It's possible?
by tokumaru on 2016-01-06 (#162003)

The MMC5 has all the features necessary to run the game, but it's not directly compatible with the game's original mapper. This means that, in addition to rewiring the hardware, the ROM has to be hacked, and all the code that deals with the mapper (bankswitching, scanline IRQs, etc.) has to be modified to work with the new mapper. This is generally not a hard thing to do, but it's somewhat tedious, and requires some programming skills.

Re: Street Fighter III (3) reproduction? It's possible?
by ramiq27 on 2016-01-07 (#162072)

tokumaru wrote:
The MMC5 has all the features necessary to run the game, but it's not directly compatible with the game's original mapper. This means that, in addition to rewiring the hardware, the ROM has to be hacked, and all the code that deals with the mapper (bankswitching, scanline IRQs, etc.) has to be modified to work with the new mapper. This is generally not a hard thing to do, but it's somewhat tedious, and requires some programming skills.

Thanks for your input. That's disappointing as I have no experience at all with programming. I guess will have to find a rom that is modified or learn how to do this myself.

Re: Street Fighter III (3) reproduction? It's possible?
by FrankWDoom on 2016-01-07 (#162073)

Would it be possible to modify a mmc3 board by repurposing an unused prg address line as another chr address line?
http://wiki.nesdev.com/w/index.php/MMC3 ... .2C_odd.29

It seems like it would be possible, but probably ugly since changing chr banks would require two bank data updates, and you'd have to keep track of the current prg bank as well so you don't change that in the process.

Re: Street Fighter III (3) reproduction? It's possible?
by lidnariq on 2016-01-07 (#162076)

No. MMC3's PRG outputs depend on what the current bank the CPU reading/executing from.

Best hopes are a mapper hack to mapper 12, 90/209/211, 33, or VRC4.

Or just building a new cartridge from scratch using programmable/discrete logic. Mapper 91's pretty simple.

Re: Street Fighter III (3) reproduction? It's possible?
by tokumaru on 2016-01-07 (#162077)

FrankWDoom wrote:
Would it be possible to modify a mmc3 board by repurposing an unused prg address line as another chr address line?

Probably not, because that would allow you to select which half of the CHR chip to use (i.e. all tiles on screen would have to come from that half), while the original mapper appears to allow selecting any 2KB bank from the entire 512KB chip.

EDIT: Also what lidnariq said.

Re: Street Fighter III (3) reproduction? It's possible?
by FrankWDoom on 2016-01-07 (#162078)

lidnariq wrote:
No. MMC3's PRG outputs depend on what the current bank the CPU reading/executing from.

Best hopes are a mapper hack to mapper 12, 90/209/211, 33, or VRC4.

Or just building a new cartridge from scratch using programmable/discrete logic. Mapper 91's pretty simple.

ok. This is a tangent but how do the larger mmc1 games get away with borrowing a chr address line to use larger prg? Is chr output always the same?

Re: Street Fighter III (3) reproduction? It's possible?
by tepples on 2016-01-07 (#162079)

They get away with it by using 8K mode.

MMC1 boards SNROM, SUROM, SOROM, and SXROM repurpose CHR address lines A16-A14 (bits 4-2 of $A000 or $C000) to control address or enable lines of PRG ROM or PRG RAM.

SNROM: A16 controls WRAM disable
SOROM: A15 switches between two WRAMs
SUROM: A16 controls PRG ROM A18
SXROM: A16 controls PRG ROM A18 and A15-A14 control WRAM A13-A12

But all four of these boards have 8K CHR RAM. This means they can either A. set 8K CHR mode in $8000, so that $A000 is used and $C000 is ignored, or B. set bits 4-2 of $A000 and $C000 to the same values. A is more practical.

Repurposing the other way would require setting the same value in one bit for all PRG banks. That's feasible when all PRG banks are switchable, which usually means mappers with 32K PRG banks. It's also feasible on a multicart mapper, where some outer bank bits may be shared between PRG ROM and CHR ROM. But it's impractical when one or more PRG banks are completely fixed. In MMC3, either $C000 and $E000 or $8000 and $E000 are fixed to the last two 8K banks in the cart.

Re: Street Fighter III (3) reproduction? It's possible?
by FrankWDoom on 2016-01-07 (#162082)

That makes sense, thanks for the good explanation.