Rumbledethumps' Picomputer 6502 Marries the Classic MOS CPU with Raspberry Pi Pico Boards

Pseudonymous maker "Rumbledethumps" is working on a project dubbed the Picocomputer 6502 — designed to bring the joys of programming the vintage MOS 6502 processor to a new audience courtesy a linked pair of Raspberry Pi Pico microcontroller boards.

"The Picocomputer explores retro computing and game development by removing the barrier between genuine 8-bit hardware and modern devices," Rumbledethumps explains of the project's goal. "I use 'Picocomputer 6502' to refer to the reference design. It is my hope that derivative projects use a different name. For example, 'Picocomputer VERA' or 'Ulf's Dream Computer.' Think about what people asking for help should call the device and go with that."

The heart of the Picocomputer 6502 is, as the name suggests, a MOS Technology 6502 eight-bit processor — or, rather, its modern equivalent, the Western Design Center W65C025. This piece of genuinely vintage hardware is then given the benefit of modern technology through the RP6502-RIA, an interface adapter designed to replace a series of chips which would otherwise be required — and running atop a low-cost Raspberry Pi Pico and its RP2040 microcontroller.

For those who want more features, a second Raspberry Pi Pico can be added to the design running the RP6502-VGA firmware — turning it into a video chip which communicates with the RP6502-RIA. "More than one VGA module can be [added]," Rumbledethumps explains. "Note that all VGA modules share the same 64K of XRAM and only one module can generate frame numbers and vsync [vertical sync] interrupts."

"Want a Picocomputer? You can build one today," Rumbledethumps says, "but be prepared for some bumps. For example, there's no breadboarding instructions. And the software selection is mostly test programs. The source code [is] not ready for a public release. However, I'll give you early access if you build a DIY Picocomputer or generously support the project on Patreon."

At its heart, the project is similar to the Neo6502 recently announced by Olimex founder Tsvetan Usunov — though the Picocomputer 6502 is considerably further along in the design process, with third parties already posting their DIY builds to the project's discussion forum and Rumbledethumps showing off a custom operating system with features not often found in 6502-based systems including protected mode operation and multiprocessing.

More information is available in the Picomputer 6502 documentation, with a YouTube playlist of videos walking through the project's progress in over the last year.