Mega Memory Card (Game Boy)

Mega Memory Card
Also known as: Mega Memory (EU), Memory Backup (JP) Publishers: InterAct (US), Datel (EU), Karat (JP) Platform: Unlicensed Game Boy Released in JP: 1999 Released in US: October 1999 Released in EU: 1999 This game has unused text. This game has debugging material.

The Mega Memory Card is a third-party Game Boy accessory which allows you to back up the SRAM save data from a game cartridge into the Mega Memory's internal flash memory. The cartridge has an upside-down cartridge slot to connect the cartridge you want to back up memory from, similar to GameShark and other Game Boy cheat devices. The device has a switch which allows you to bypass the Mega Memory software and run the game on the cartridge in the second slot.

The device comes in two different styles: a yellow semi-transparent cartridge, and a black glittery cartridge which was sold in French-language packaging. The black shell was also kept for the Japanese release, which (as expected) localizes the device's menus.

One peculiar aspect of the device is that it uses a trick to switch the cartridge base memory area during the boot process to display a custom logo in the startup animation instead of the usual Nintendo one.

To do: Check if anything else was changed in the Japanese version.

Factory Test Screen

Hold Select + Start + B + A while the cartridge is booting. The test screen attempts to query the internal flash chip for its ID, as well as enumerate the SRAM banks in the secondary cartridge. The correct value is 04BF, which corresponds to the SST 28SF040 EEPROM/flash memory in the cartridge. If the debug screen is executed in an emulator, the result will likely be 3EC9, which corresponds to the first two bytes in the program ROM.

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  The factory test screen as it looks when running without modification in BGB.

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  Simulation of what the screen looks like on real hardware, with no secondary cartridge inserted.

Mushroom/Kingpin

The Mega Memory uses the 16-byte string "Mushroom/Kingpin" ($2848-$2857 in the ROM) as a test string to determine whether there is writable SRAM present in the secondary cartridge. It is unknown whether this is a purely random choice of words or a reference to something, such as a greeting to a member of a scene group. This string appears to not be accessed anywhere else in the ROM.