Software-Defined ROM's Latest Version: The Current Manifestation

Piers, a developer known for his work in the retrocomputing community, has announced a new product called the One ROM. This innovative solution is designed to replace failing ROMs in old Commodore gear, offering a modern twist to classic hardware.

The One ROM is built on a two-layer PCB, featuring the RP2350 microcontroller at its core. Unlike the larger STM32 used in the previous version, the PCB layout for the RP2350 necessitated extensive changes. The RP2350, with its large power and ground pads underneath the IC, previously served for signal routing, but that area is no longer available due to the RP2350's design.

Piers initially wanted to use the RP2350 but couldn't due to lack of space on the board for level shifters. However, the A4 stepping added 5V tolerance, allowing Piers to reformulate his design and make the One ROM 5V capable.

The One ROM's firmware is performance critical and needs to convert requests on the address pins to results on the data bus as quickly as possible. To meet these requirements, Piers employs a number of tricks in the design process.

Interestingly, the C64 in the demo uses three different ROMs: basic ROM, kernel ROM, and character ROM. Remarkably, a single One ROM can emulate all three ROMs in the C64.

For those intrigued by the design process and the trade-offs made in the project, an accompanying video from Piers provides valuable insights. The video offers a behind-the-scenes look at the development of the One ROM, providing a fascinating glimpse into the world of retrocomputing.

The One ROM's code is available on GitHub for anyone interested in delving deeper into the project. The developer of the latest One ROM built with an RP2350 for retrocomputers is not explicitly mentioned in the available search results, but the open-source nature of the project allows for community collaboration.

Piers wrote in to inform about the new version of his project, marking an exciting development in the retrocomputing community. The One ROM is set to revolutionise the way we handle old Commodore gear, offering a modern, efficient, and sustainable solution.