How I Built a CPU for Fun (and Didn’t Learn Verilog)

Python can run on a regular computer or on a general purpose microcontroller. But as a hobbyist, I was curious about how to design a completely custom device, which led me into the FPGA world. Traditionally, FPGA programming requires learning VHDL or Verilog, but there’s a Pythonic alternative: Amaranth. This powerful open-source library lets you describe digital circuits in Python and load them into affordable FPGA boards. In this presentation, I’ll share a high-level look at the development process using Amaranth, as well as provide demos, including one of a simple CPU built from scratch. If you’re curious about hardware or eager to explore beyond software, this talk will show how Python can open that door.

This talk is an invitation to explore hardware through the lens of Python. I'll share my journey as a software engineer stepping into the world of FPGAs — not through Verilog, but via Amaranth, a Python-based hardware description library. I’m approaching this as a hobbyist curious about expanding my knowledge and building fun toys, rather than polished products — though Amaranth is certainly powerful enough for “real” projects.

I’ll walk through the tools and process I used to build a small homebrew CPU, inspired by the SAP-1 from Malvino & Brown’s “Digital Computer Electronics.” We’ll look at how to write and integrate design components, interface with a Tang Nano FPGA board, and connect to external hardware. I’ll share photos, videos, and — live-demo gods willing — a real working device.

This session isn’t a step-by-step tutorial, but a guided tour meant to spark your curiosity. If you enjoy Python and like building things, you might just discover a new playground.