These are official Game Boy flash cartridge sold in Japan. You would go to a designated flashing station and have your cartridge flashed for a cheap price.
The cartridge is marked DMG-MMSA-JPN and the board is marked DMG-A20-01 (I’m not sure whether the character after the 2 is a zero or upper case o – I’m actually leaning towards the latter as it appears to be a little bit wider than the following 0)
The board contains three intergrated circuits.
- 29F008ATC-14 – 8 Mbits (1 Mbyte) flash ROM. I can’t find a datasheet for it, so I’m guessing it’s a custom or OEM chip. I’ve seen Mask ROMs/OTPROMs in game cartridges also marked MX, so Nintendo probably had a contract with them.
- UT621024SC-70LL – 1Mbit (128 kBytes) of battery packed save RAM.
- MX15002UCA – Custom logic chip marked G-MMC1. The apparent function of this chip is MBC like functionality. Maybe there’s more to it too, like the ablity to offset the ROM and RAM addresses for multigames or flash memory protection? Details unknown. There’s an unused place for a crystal.
Note the square boxes on the back side, of the PCB, on the opposite side of the connector that goes into the cartridge header. These were most likely used in the factory to program the cartridge initially. Notice how the “unimportant” system clock and external audio inputs are missing this box. Also note the nice rounded PCB traces. Not often you see these. Visually appealing, indeed.
And maybe it’s a sign I’m getting too little sleep that I’m seeing a “face” in the image.
The scans are provided by Duo.