One ROM is a ROM/EPROM replacement solution for computer systems from the late 1970s to the early 1990s. It is built around low-cost microcontrollers, open-source hardware, and companion software tools. It can emulate 24-, 28-, 32-, and 40-pin EPROMs and mask ROMs, with the goal of replacing aging or rewritable original ROMs in vintage computers, disk drives, arcade machines, and similar devices.
Its biggest strength is flexibility: hardware with the same pin-count version can be configured to replace multiple ROM types, and it supports software-configurable chip-select behavior, reducing the need to make different PCBs for different systems. It can store multiple ROM images selectable via jumpers, and also supports dynamic bank switching while the host system is running. The USB version can be programmed directly in a browser in about 10 seconds without a standalone programmer; the Pro/SWD method enables runtime image switching, telemetry reading, and further expansion.
The firmware is written in C and hand-optimized assembly, while the Fire version also uses the RP2350βs PIO to improve ROM response performance. The management tools are mainly built with Rust async, and the web version combines WebAssembly, WebUSB, and JavaScript. The toolset includes One ROM Web, CLI, and Studio, aimed respectively at beginners, advanced users, and experts. The project has been tested on systems such as the Commodore 64, VIC-20, PET, BBC Micro, Apple II, Atari 800XL, TI-99, and CoCo2, and provides GitHub resources, a Visualizer, firmware images, tutorial videos, and a discussion forum.
One ROMβs hardware designs, firmware source code, build tools, and documentation are fully open source, with licenses that allow modification and commercial manufacturing. Cost information is transparent: the microcontroller costs under US$2, small-batch PCB production is under US$10, and volume production is under US$5. However, the main text does not disclose pricing for finished boards or available payment methods.
Its advantages include low cost, a high degree of openness, complete documentation and manufacturing files, broad system compatibility, and USB programming that lowers the barrier to entry. Its limitations are that it is a highly specialized vintage-hardware tool, and advanced features still require knowledge of SWD, firmware, and electronics debugging. Some ROM types may also not yet be fully supported on every board. It is best suited to vintage computer repairers, hardware hackers, firmware developers, and open-source hardware enthusiasts.
The site is hosted on GitHub Pages, and the main text does not provide information about access from mainland China, logistics, or payment options, so its China access status is rated as unknown. If access to GitHub resources is unstable, users may need to resolve network issues themselves; information about buying finished boards and alternatives should also be checked further on the Buy page or in community discussions.
β This review is compiled from public sources and does not constitute a purchase recommendation. Verify all facts on the vendor's official site. Verify on onerom.org official site.
onerom.org is an Unknown Dev Tools provider. TG4G tracks its product information, with monthly pricing from $5.00, an overall rating of 6.0/10, and a China-accessibility score of China direct-connect friendly. Click "Visit Official Site" to reach onerom.org directly.