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MBC1 (Game Boy mapper)

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MBC1 is a licensed Game Boy chip and Game Boy mapper by Nintendo and Sharp, with memory bank controller support.

It is among the first Game Boy mapper chips; for basic games (and graphics, performance) before the release of the Game Boy Color. As only 32KiB of ROM can be accessed at a time, the MBC1 (Memory Bank Controller-1) is used to access 16KiB areas in banks beyond that position (so 2:4000 would map to 0x8000) and so on. Games using this mapper can include those with Super Game Boy enhancements.

Certain games such as Alleyway do not require the MBC; they can only access up to 1:4000-1:7FFF; which is the last offset of their ROM size; 32KiB).

In order to change ROM banks in a game that supports the MBC1 (and others like MBC2, MBC3, etc.), the Game Boy CPU will act as if it is writing the contents of the accumulator (a) to 0x2000-0x3FFF in the ROM; in order to change to the bank matching the hexadecimal value in the accumulator (but may be subjects to design flaws beyond bank 1F in MBC1 (and MBC2). MBC1 can support ROMs up to 2MiB size and RAM sizes up to 32KiB, but due to a design flaw or bug ROM banks 0x20, 0x40 and 0x60 cannot be used. 125 ROM banks can be addressed.

Some Game Boy games/software with this chip use different wiring for an external RAM mode (known as MBC1-M), and this might be why games like Pokémon Red and Green Versions can have save battery functionality in relation with this chip; usually from a button cell), as opposed to other means of saving progress like a password (though games without the MBC can still have external RAM). MBC1/MBC1-M supports external RAM/save files between 2KiB-8KiB (for the largest 8KiB/32768 bytes, this can be split using four SRAM banks in blocks of 0x2000 bytes size each).

Even though MBC1 was designed originally for the Game Boy, later MBC1 games have Game Boy Color enhancements such as Tetris DX.

Nintendo-published games with this mapper

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Game Boy Wars and Game Boy Wars Turbo also use this mapper, but were published by Hudson, however Nintendo also own rights to the Wars series.

External links


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