Picocomputer 6502

  • Arrows move. Space, up, or down fires. Gamepads work too.

  • 1 one player, 2 two players, p pause, r restart.

Why a Picocomputer

Modern computers are astonishingly powerful, and that power creates distance. Write a few lines of code and you’re immediately standing on top of millions of lines of software — enormous APIs, operating systems, frameworks, layers of abstraction. AI makes that distance greater still: you can ask a machine to produce something impressive without necessarily understanding what happened.

The Picocomputer goes the other way. It’s simple enough to learn completely, and every layer under your program is documented on this site for you to take on one at a time.

It’s also powerful enough that you won’t outgrow it. Your 6502 program drives a video system and a sound system modeled on the arcades and home computers of the 8-bit and 16-bit era, with far more headroom than those machines ever had. Your game can throw hundreds of sprites across the screen and pull in megabytes of art and music.

Write a Game

Start from the project template, open it in VS Code, and press F5. Hello world builds and runs in the emulator, with breakpoints and a call stack. No hardware, and nothing to buy.

When it’s good, edit a couple of lines and upload it to itch.io, where anyone can play it in a browser.

RP6502-SDK has the details, from installing a compiler to debugging on real hardware.

The Whole Machine

  • CPU — WDC 65C02 and a 65C22 VIA, 0.1 to 8.0 MHz, cycle accurate on every host

  • Memory — 64 KB of RAM and 64 KB of XRAM, loaded by DMA at up to 800 KB/sec while the 6502 keeps running. No ROM, nothing reserved, and zero page is yours

  • I/O — 32 registers, and that’s all of them. A modern processor sits behind them running the USB, the files, and the network, so the 6502 never has to

  • Video — three planes of tiles, bitmaps, and sprites in RGB555, programmable per scanline, with affine transforms on 16-bit sprites

  • Sound — eight 48 kHz oscillators with ADSR and stereo panning, or a 9-voice OPL2 FM

  • Storage — USB flash drives, and 3.5-inch floppy drives if you have one

  • Input — keyboards, mice, tablets, and four gamepads, over USB or Bluetooth

  • Also — Wi-Fi, MIDI, a real-time clock that handles Daylight Saving, and a true random number generator

All of it is documented on this site, down to the register.

Get a Machine

You already have one. Games and applications are distributed as .rp6502 ROM files, and every machine runs all of them.

  • RP6502-EMU — the browser, Windows, macOS, Linux, Android, and RetroArch. Free, and where you start.

  • RP6502-PICO — the one you build. 100% through-hole, no IC programmer, and you don’t even have to solder — but you will plug eight ICs into their sockets. Usually under $100 USD.

  • RP6502-FPGA — the whole machine in gates, on an Analogue Pocket today and MiSTer next.

Community

Most of the action is on Discord, where you can also grab ROMs. Subscribe to the YouTube channel and share the project around while you’re at it.

Read the Docs

  • RP6502-SDK: writing software, from a new project to a running program.

  • RP6502-RIA: the register map and every device reached through it — the interface adapter, in the spirit of the classic CIA, VIA, and ACIA chips.

  • RP6502-RIA-W: setting up Wi-Fi, Bluetooth, telnet, and the Hayes modem.

  • RP6502-VGA: canvases, video modes, sprites, and the scanline programming underneath.

  • RP6502-TERM: the console, its escape sequences, and the line editor.

  • RP6502-OS: the system calls, the ABI, and the C library sitting on them.