GBneprio is a classic Game Boy cartridge built around just two active chips: a 16 Mbit (2 MB) NOR flash ROM and an Atmel ATF1502AS CPLD that implements the bank-switching logic. The mapper is a hybrid of Nintendo's MBC5 and MBC1 behaviour, derived from insideGadgets' original design and retargeted to the ATF1502 in Verilog.

The deliberate minimalism is the point. With no SRAM, no battery and no discrete glue logic, the board draws very little current and costs very little to populate — five surface-mount placements in total, all on the top side.

The 32-contact cartridge edge connector is etched directly into the PCB as gold fingers, so gold plating is required. The CPLD is programmed in-system through a Würth SKEDD solderless press-in connector, which means no programming header is soldered to the board; you need a JTAG programmer such as the Atmel ATDH1150USB and a separate 5 V supply while flashing. The board is designed to drop into a donor Game Boy cartridge shell, and its outline already carries the required notches and cut-outs.

One thing to watch: the board must be fabricated at 0.8 mm thickness, even though the design files declare 1.6 mm.

This package is a share of an existing open-source project, not original work. The design is by na103 and the upstream repository is at https://github.com/na103/GBneprio — please go there for the canonical source, issues and updates. The author accepts tips at ko-fi.com/na103.

Note that the project's licence is ambiguous: the README states CC BY 4.0 while the bundled LICENSE file is CC BY-NC-SA 4.0. Check with the author before any commercial use.