m6502, a 6502 CPU for FPGAs and Tiny Tapeout
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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.
HN · launched Feb 18, 2026 · 5 upvotes (top 89%) · 0 views
Niche: open-source hardware and maker electronics · 180 launches, 3 in the last 7 days ▼ -73% · Explore this niche →
Category and tags
- Horizontal
- Hardware & robotics
- Developer
- Not AI
- Hobby / open-source project
Visit website ↗ Source listing ↗
More like this: all 180 launches in open-source hardware and maker electronics →
Could you build this?
No Developing a cycle-accurate hardware CPU core in HDL (Verilog/VHDL) targeted for ASIC tapeout requires specialized electrical engineering and digital circuit design expertise.
What it would actually take: The implementation requires writing Verilog or SystemVerilog that accurately models every cycle, bus transaction, and internal state register of the MOS 6502, verified against formal test suites. For Tiny Tapeout, it must pass strict DRC/LVS checks and synthesize within extreme gate count and pinout limits using open-source EDA tools like OpenLane and Yosys. This requires specialized knowledge of digital logic synthesis, hardware timing closure, and silicon layout design.
Discussion
1 comment analyzed.
Competitors mentioned: cocotb test benches, Klaus functional tests
Concerns raised: Test coverage gaps between simulation and physical hardware, IRQ servicing edge cases not caught by tests
Competitors
Other products that read as similar to this one : 325 launches clear the similarity bar, closest 8 shown.
Attention rank: #302 of 326 (itself plus its competitors, highest first, normalized so YC and Product Hunt are compared fairly).
Launched 112 days after the earliest competitor.
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