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Gameboy 4MB 32KB FRAM MBC3 with RTC Flash Cart (Works with Pokemon games/hacks like CC)


Usually MBC3 chips only allow for 2MB of flash however by adding a special logic chip, we can extend the flash size to 4MB so you can future proof your RTC cart.

Only a few carts will be made each month due to the various steps required to build them.

We highly recommend you purchase a flasher so you can backup your save and re-flash the cartridge with newer updates of games. Re-flashable with any flasher like GBxCart RW that supports the MBM29F033C chip via the audio pin method. Uses FRAM to keep the save even when the battery runs out. Designed and made in Australia.

The blue cart will only fit in original DMG style or GBC style cart shells (GBC style requires 2 small cuts), won’t fit in Japan Crystal shells.
The pink cart will fit the following shells – DMG, GBC, Crystal (Japan/USA) and Kirby check the pictures. It can also fit the Boxy Pixel shell but requires the capacitor next to the flash chip to be removed (and placed above it).

If you would just like a regular 4MB cart, you can proceed with the default options we’ve set. This cart works on every Gameboy system – GB, MGB, GBC, GBA, GBA SP and the Game Boy Player. It also works on the N64 transfer pack for Pokemon Stadium 1 & 2 (as per a user report).

SKU: N/A Category:


New v1.2 PCB allows for Rumble (supply your own motor, requires game patching to use, check example) and 2x 2MB ROM Mode which allows you to switch between 2 ROMs such as Gold/Silver to share the same save file (shell cutting/trimming is required to fit the switch, the shell won’t close unless you trim the top part of the shell but be sure not to cut the little notch).

How to use the rumble motor
You need to write the byte 0x20 to 0x4000-0x5FFF. Usually games write 0x08 but that would conflict with the RTC so you need to patch games to use 0x20 instead. For Pokemon Pinball we have an example patch to apply but it doesn’t appear to activate the rumble strong enough – you could lower the resistor if need be.

How to use 2x 2MB ROM Mode
Check the picture as you need to bridge jumper pads with solder and un-bridge another jumper pad. You’ll also need a special program to flash both ROMs to the cart: 2x 2MB ROM Mode Flasher v1.1.

ROM: 4MB Flash (MBM29F033C)
FRAM: 32KB (Data retention of 20-50 years)
MBC: MBC3 original chip

The power consumption of MBC3 when powered from the battery appears to be around 2.3uA so a CR2025 should last 5-7 years and a CR2032 should last around 7-10 years.

The PCB finish is ENIG.

If you will be installing this flash cart in an original shell, it is very difficult due to the CR2032 battery holder but it is possible, some users prefer using a CR2025 battery holder instead.

Additional information

Weight 10 g
PCB colour

Blue, Pink/Berry


RTC, RTC and Rumble components (no motor)

ROM mode

4MB mode, 4MB mode (populate switch, shell cutting required), 2x 2MB mode (populate switch, shell cutting required)

Cart Colour

Grey, Clear, Clear Blue, Clear Green, Yellow

Battery & holder

CR2025, Holder only (no battery)

Pre-loaded ROM

I will provide a ROM to flash by email, Not required or N/A

Flash carts

Gameboy carts, Low power, MBC3 support, RTC support, Saving supported


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