A lot of great games for the MSX home computer use a Konami4-style memory mapper for 128kB/MegaROM games.

Titles like Nemesis, The Maze of Galious, and Metal Gear use this mapper, and will not work with just a bare ROM cartridge. Most advanced multicarts support this mapper, but they are also very expensive and difficult to hand-solder.

This cartridge implements the basics of the Konami4 mapper, supporting these games.

This cartridge PCB was built as part of a Leaded Solder blog project. More details are available at the Oyanami GitHub repository.

Ordering notes

I strongly recommend getting hard gold or ENIG plating, and checking the "edge connector" options where possible, especially the bevel.

This will make the cartridge more durable than tin fingers over the long term.

Usage notes

The active game can be switched between one of four options by toggling the position of the DIP switches on the front of the case.

Assembly notes

In order to populate the games on the cartridge, you must have an EEPROM writer such as TL866 or T56 in order to program the SST39SF040, prior to soldering it. It is not currently possible to program the contents of the cartridge once assembled.

Writing the ROM should consist of four 128kB games one after the other to produce a total ROM size of 512kB (4 megabits.) You can use cat on Unix systems to do so.

Make sure that you are using a 74LS670 - ALS has been reported not to work on Turbo-R MSX systems.

Socketing the SST39SF040 may make the PCB too tall to fit into most MSX cartridge cases, so it is recommended that the ROM be soldered directly to the board after programming. You may consider making a socketed board for testing the ROMs.