The web is full of guides, tutorials, and hardware accessories for backing up Game Boy, Game Boy Color, and Game Boy Advance games. However, the modder and youtuber known as TheZZAZZGlitch decided to explore a more chaotic alternative route: freeze a Game Boy Advance game and rebuild it from the sound produced by its errors. The process demands hours of recordings and fixing multiple bugs, but there's a lot to learn here.
The Game Boy family has many strong points; one of them is the relative robustness of its cartridges, though they're far from immortal. Depleted batteries, connector friction, moisture, drops, and PCB flex are some of the causes that can knock a cartridge out, throwing all sorts of errors. But what if we cause those errors ourselves?
The YouTuber TheZZAZZGlitch is dedicated to exploring glitches and hacks in the early generations of Pokémon games. In other words, freezing Pokémon games is his specialty. In one of his latest videos, “TheZZAZZGlitch” explained the sound of the crash or freeze on the Game Boy Advance, and he suggests that the entire contents of the cartridge can be reconstructed using only that audio….
The Game Boy Advance, Singing the Song of Its People
Long story short, the Game Boy Advance's sound is transmitted through a small buffer in RAM using DMA. When it reaches the end of the buffer, an interrupt triggers to refresh the data and send the DMA pointer back to the start. However, during a crash, the interrupt is lost and the DMA pointer never gets reset, meaning it keeps sending the entire contents of memory to the speaker as if it were sound.
After waiting almost two hours, TheZZAZZGlitch obtained an 8-bit sound at 13.1 kHz. With the help of a Python script (and the effort of spending two days fixing bugs), he managed a 99.76 percent reconstruction... although that wasn't enough. By combining three recordings with a majority vote algorithm, accuracy rose to 99.979 percent. The ROM booted in the emulator, but still had too many errors. The key? More recordings: With seven different dumps, accuracy reached 100 percent, completely restoring the ROM.
The second half of the video focuses on repeating the process using real hardware, and as an extra flavor, a fake Pokémon Emerald cartridge. In this case, he needed 45 recordings, and even then didn't reach 100 percent (99.9837%), but the game booted correctly. To finish, the cartridge had a surprise: By using no battery or dedicated chip, the savegames are stored in the same flash memory where the game was placed. Someone did a great job hacking that fake cartridge, and TheZZAZZGlitch will likely explore it more closely in the future.
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