Show HN: m6502, a 6502 CPU for FPGAs and Tiny Tapeout
chrismoos Wednesday, February 18, 2026
Hey HN,
Recently built an Apple II emulator and at the same time was getting into Tiny Tapeout and decided it would be cool to build a cycle-accurate 6502 CPU and an MCU for it. It's cycle accurate and the core itself should be 100% compatible with a stock MOS 6502 (would need to still test this though!).
Tested on some FPGAs (fomu, ulx3s) and works great, hoping to get it taped out in the upcoming IHP26a shuttle.
Also as part of the project I built a bus multiplexer to allow memory/bus access from an RP2040 to work around the limited pin count on Tiny Tapeout. This let's you load up programs on RP2040 and the CPU can read/write from it.
Summary
The m6502 project is an open-source emulator for the MOS Technology 6502 microprocessor, a widely used chip in early microcomputers and gaming consoles. It aims to provide a reliable and accurate implementation of the 6502 architecture, enabling developers to build applications and games that run on this classic processor.
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github.com