MROM: A New Tool for Game Boy Cartridge Preservation via an Analogue Pocket

MROM is a new project developed by Noel, with contributions from agg23, designed to help collectors preserve their physical GB/GBC cartridges, specifically for use with the Analogue Pocket console.

The tool provides a simple way to manage your collection:

• Extract Game Data (Dematerialize): You can pull the full ROM content from the cartridge and store it on your SD card.
• Manage Savegames: Easily retrieve, back up, or reupload save files (.SAV) between the cartridge and the Analogue Pocket’s SD card.
• Check Cartridge Details: View essential hardware information, including the ROM/RAM size and the Memory Bank Controller (MBC) type.

Technical Foundation

MROM is built on a custom, modern technical architecture, making it a continuation of Noel’s previous work on a cartridge interface.

Feature	Technical Detail
Processor Core	The project is built around a RISC-V core, utilizing the work by agg23 to integrate this powerful open-source processor architecture into the Pocket environment.
Hardware Framework	MROM uses a WISHBONE compliant cartridge interface and relies on the LiteX framework for handling the underlying hardware signals.
Speed and Timing	The entire system is kept synchronized by basing its timing on the classic, single-speed Game Boy clock (4.194304M/4). Data is copied quickly from the RISC-V core’s memory, with the CPU automatically slowed by wait states when necessary.

The firmware is a very small, self-contained program that runs on a custom multitasking core, currently supporting features like full MBC2 management and aiming to expand to MBC1, MBC3 (including Real-Time Clock features), and MBC5.

An MBC (Memory Bank Controller) is a chip that lets the game access more memory than the Game Boy normally supports by switching different sections of ROM or RAM in and out as needed. MBC1 was the first widely used version and allowed larger games with optional save memory. Later versions, like MBC2, MBC3, and MBC5, expanded on this with built-in RAM, real-time clocks, or support for much larger game sizes. In essence, MBCs act as memory managers that make bigger and more complex Game Boy games possible.

The gateware (hardware description code) is available on GitHub under the openfpga-litex repository, but Noel is currently retaining control of the firmware to manage its development. The developer stresses that MROM is intended for educational and preservation purposes only.

The MROM project and its documentation with full details are available here.