March 18, 2026
Blink if you’re debugging
Write up of my homebrew CPU build
From glow-up to glitch: DIY CPU sparks ‘simulate vs solder’ smackdown
TLDR: A homebrew 8‑bit CPU hit real hardware with lots of mistakes and blinking lights. The community split: some say skip physical builds and keep it simulated, others celebrate the chaos and push for a tiny chip version—plus lots of nerdy tips to speed up and clean up the design.
A brave builder took their home‑made 8‑bit computer from the comfy world of simulation to the messy reality of wires and blinking lights—and the crowd went wild. The post is equal parts hero shot and horror story: backwards LEDs, haunted memory chips, and learning binary by staring at blinks because an output display wasn’t built yet. Cue the chorus: Is this art or pain?
The loudest camp is pure pragmatism. artemonster warned to skip breadboards and real hardware entirely, arguing physical builds turn fun into “glitchy half‑dead chip” stress. Meanwhile, tinkerers cheered the red‑light aesthetic and shared gear love—jacquesm swooned over the builder’s Rigol oscilloscope—while others went full advice mode, from smarter register tricks to faster memory programming. One commenter even asked the existential tech question: komali2 wonders how the very first CPUs were programmed, musing about the ultimate chicken‑and‑egg.
And then came the moonshot: Taniwha nudged the maker to try a “tiny tapeout” and etch the design onto a real sliver of silicon. Between the builder’s slow‑but‑working EEPROM writer (a memory chip writer) and a confession that surface‑mount parts don’t play nice with breadboards, the crowd split into two vibes: simulate it to save your sanity, or embrace the chaos and keep those blinkenlights blazing.
Key Points
- •The author moved from a Logisim-Evolution simulation of an 8-bit CPU (WCPU-1) to building a hardware prototype.
- •Schematics were created in KiCad; parts were ordered from DigiKey with an initial SMT-focused plan that clashed with breadboard prototyping.
- •Three PCBs were ordered from PCBWay, including an EEPROM Programmer Board needed to program microcode ROMs.
- •The EEPROM programmer uses an Arduino Nano and shift registers; a design mistake routed OE/WE/CE through shift registers, limiting write speed and preventing page writes.
- •Single-byte EEPROM writes took ~80s for 8KB versus ~1.3s with page writes, but the slower approach worked on the first try.