Even with a 3D-printed housing and some considerable refinement since revealing the idea a few months ago, Alfonso’s custom emulation cartridge is still bulky as far as GBA carts go, but it cleverly leverages the GBA itself as an all-in-one portable display and controller. One of the best features of the GBA was that it allowed two handhelds to be connected for multiplayer gameplay even if only one system had the actual game cartridge. Hackers have long since reverse-engineered how this multiboot feature worked, and Alfonso uses it to send a 240×160 (the limited resolution of the GBA’s screen) video stream through the Game Boy Advance’s link port.
Alfonso has also shared a video on how the whole thing was built, and the custom code needed to run on the GBA itself is available for download on their GitHub page. And while the custom cartridge works on an unmodified Game Boy Advance, the GBA featured in these videos has two upgrades: a backlit LCD screen as well as some extra hardware that actually overclocks the handheld’s CPU to increase the data rate through the link port, improving the streamed frame rate and playability of the setup.