nesdev.org

Hi.

I just found that there are flash memory on a cheap "coolboy" cartridges (about $3). So I can rewrite it! All you need is to unsolder /RD and /WR pins. So I can use my dumper with JTAG connector.
Video (russian language, sorry): https://youtu.be/5_XZyVoEzE0?t=4m46s

So it's possible to create very large (32 megabytes) multirom cartridges for MMC3 games using ultra cheap $3 chinese cartridges.



It's just awesome.

How does the menu select which game to play? The MMC3 only supports 512 KiB (or maybe 2 MiB), and none of the documented multicart mappers go above 4MiB ... so how does it address 32 MiB of flash?

What is the exact name of the chip?

lidnariq wrote:How does the menu select which game to play? The MMC3 only supports 512 KiB (or maybe 2 MiB), and none of the documented multicart mappers go above 4MiB ... so how does it address 32 MiB of flash?

It's "COOLBOY" MMC3-based mapper. It has additional registers. You can view it in fceux source code: http://sourceforge.net/p/fceultra/code/ ... oolboy.cpp

FARID wrote:What is the exact name of the chip?

"COOLBOY". It's UNIF mapper in fceux. You can find this cartridge as "coolboy 198 in 1" or "coolboy 400 in 1" on eBay or aliexpress.com.

That is a pretty cool multi-cart creation.

I watched the video with transliterated captions but it's difficult.

I've been tinkering with Coolboy carts for a while. but I'd never worked out how to rewrite them.

How do you change the game names, build the multiROM etc? Will you make tools available?

GameMachineJames wrote:I watched the video with transliterated captions but it's difficult.

I've been tinkering with Coolboy carts for a while. but I'd never worked out how to rewrite them.

How do you change the game names, build the multiROM etc? Will you make tools available?

Hate to make a me-too reply, but yes, inquiring minds want to know!

Seriously, though, this is a great find. I've been wondering about the GBA games with the adapter daughterboards for a while, now. I have assumed that most of the pirate carts aren't Mask ROMs but since I don't have any FC/NES pirate carts, I can't try this just yet.

It'll be very like any other multicart. The registers are set by hardware to specific values on power-up (and maybe on reset), and the ordinary NES code there is responsible for everything needed to switch games.

It'd make a good "My First NES project", if it weren't flagrantly endorsing copyright infringement.

but how does it handle PRG and CHR? If there is only 1 chip for data (the other is some kind of mapper i'd assume), how can it run both busses?

getafixx wrote:but how does it handle PRG and CHR? If there is only 1 chip for data (the other is some kind of mapper i'd assume), how can it run both busses?

There are 128KB/256KB (depends on revision) of CHR RAM. Game loader loades all CHR data to RAM before game starts.

What disappoints me is "hardware tested logic, don't try to understand lol" in FCEUX's mapper source. That doesn't look very reassuring for someone planning to make and sell homebrew games.

The COOLBOY carts support four each different PRG and CHR banking modes. For a new game, you can safely just use the "obvious" (MMC3-like) one and ignore the weird modes.

Is there any reason why one couldn't use a clamp-on pin header over the PRG itself and reflash without desoldering?

There will be an address bus conflict between the chip-on-board mapper IC and the programming hardware. It might work anyway, but it's not good practice.

lidnariq wrote:The COOLBOY carts support four each different PRG and CHR banking modes. For a new game, you can safely just use the "obvious" (MMC3-like) one and ignore the weird modes.

MMC3 with 128K CHR RAM would be wonderful as a start. But wouldn't that limit each game to 512K, the maximum size of an MMC3 PRG ROM image, wasting the other 31.5 MB of the flash? I imagine that there is an outer bank register controlling which 512K is visible to the running MMC3 program, but what explains how to set the outer bank? There appears to be nothing about this mapper on wiki.nesdev.com.

Or is it like "forging your own lightsaber", where it is considered normal and just that understanding FCEUX's code is part of the price of admission to the other 31.5 MB of the flash?