Nintendo's Game & Watch hacked and turned into retro emulation beast — Solder job unlocks device from its Zelda-only cage thanks to a custom SD card slot

Source: Tom’s Hardware

Image credit: Macho Nacho Productions

Before there ever was a Game Boy, Nintendo had the Game & Watch, the company’s first successful handheld that invented the D‑pad. Since the original Donkey Kong Game & Watch, Nintendo has issued modern re‑releases, most recently the Zelda edition in 2021 to celebrate the franchise’s 35th anniversary. On Zelda’s 40th birthday, an enthusiast modded that Game & Watch into a full‑blown retro emulator.

Modding the Zelda Game & Watch

Watch on YouTube

Hardware Modifications

An ST‑Link V2 programmer was soldered to the motherboard pads, enabling communication with a computer to retrieve and modify the firmware. After flashing the custom firmware, the memory chip was upgraded.

The next step was adding a microSD card slot so the device could read external storage. This required soldering each contact of a custom ribbon cable directly to the CPU, with the ribbon already populated with a capacitor and the microSD slot.

Image credit: Macho Nacho Productions

With external storage available, the final hardware tasks were:

• Re‑soldering the speaker wires.
• Cutting a slot in the back shell for the microSD card (using a 3D‑printable jig, then sanding for a clean finish).

Image credit: Macho Nacho Productions

Software and Emulation

The mod runs Retro‑Go, a popular firmware with a modern UI and extensive console support, including:

• Sega Genesis
• TurboGrafx‑16
• And many others

Games load from the microSD card, and the sharp display renders them with vivid colors. Retro‑Go also provides save‑state functionality, making the handheld feel like a DIY Miyoo Mini that fits in a pocket. Despite its tiny size—smaller than a Game Boy Pocket—it can emulate that system as well.

Image credit: Macho Nacho Productions

The controls are responsive, and the device supports homebrew software. Battery life was not discussed, but it is expected to be similar to the stock Zelda Game & Watch.

Pros, Cons, and Alternatives

Pros

• Portable retro‑gaming handheld with a high‑resolution screen.
• Supports a wide range of consoles via Retro‑Go.
• Save‑state capability for on‑the‑go gaming.

Cons

• Requires advanced microsoldering skills; not a beginner‑friendly project.
• Battery life information is lacking.

Alternatives

If the required expertise is a barrier, pre‑modded Game & Watch units are available from some community members. For those who prefer a ready‑to‑play device, consider an Anbernic handheld, which offers greater power and out‑of‑the‑box functionality.