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2 layers202.5 × 144.2 mmFulladder, the printed circuit board in 3D

8-Bit Relay Computer inspired by Harry Porter and DipDot

Size
202.5 × 144.2 mm
Copper layers
2
Thickness
1.6 mm
Parts
162
Nets
318
Pads
814
Tracks, vias
2,173, 85
Routed
Yes
KiCad
KiCad 9.0 (file 20241229)
Created
25 Jun 2025
Updated
1 Oct 2026

Overview

Fulladder is an open-source printed circuit board by Syntaxer04, from the Syntaxer04/RC1Computer repository on GitHub, published under the GPL-3.0 licence. It is a 2-layer board of 202.5 × 144.2 mm with 162 parts on 318 nets, routed with 2,173 tracks and 85 vias.

Its parts include 79 diodes, 59 switches, 21 resistors, 2 connectors and 1 IC.

README

README.md

RC1Computer

8-Bit Relay Computer inspired by Harry Porter and DipDot

General Information

This Computer, inspired Harry H Porter III, Ph.D, Paul Law, and Youtuber DipDot, is (almost) completly made out of relays, 607 of them to be exact.

Specifications

  • 32 kb RAM
  • It has 11 15 8 Bit Registers. Some of them can also funtcion as 16 Bit Registers.
  • A clock rate Between 3 and 8 Hertz
  • 8 Bit Data and Instruction Bus, as well as an 16* Bit Adress Bus *only 15 bits are actually used, but the 16th Bit is still usable for other Peripherals/More Memeory

Changes in V0.2

  • Changed how I managed the Bus on the RC-1. The Bus Board now encompasses all Register Signals and otherwise, except for the Timing pulses, which is only used by the Controller.
  • Caught most the Routing mistakes I made in the first Version. The second run really helped spotting obvious and not so obvious mistakes.
  • Added a board for the front panel functions. The switches are not mounted on the Board however, and so are the LEDs.
  • I also started experimenting with Capacitor Storage. I included my initial design in this version.
  • The memory board had an overhaul, with more isolation and better logic.
  • The ALU has been split into two boards. I was able to do this because of the new backplane.

Future features

  • I want to make some sort Storage medium. A Tape interface, similar to DipDot's design, would be nice, although for a computer like that kind of lame in my opinion. I am thinking more like a paper based interface, like the one Usagi electric build for the UE1. One Slight Problem thogh: Reading may be somewhat easy, the writing on the other hand may be a little challenge... We'll burn that bridge when we get there.
  • Tape Loader has been added, function not Tested however.
  • The Second thing i want to make for this project is some sort of Serial/ Terminal output. That itself is not that hard all things considered, it's nearly a chip solution. The real problem is that the Computer most likely lacks any sort of speed for that kind of outpu. So i either have to buffer the output, make it exceptionaly slow, or find some other way of sending a serial signal of of the Computer.

Links

Paul Law´s Youtube channel, and his personal Blog. Harry Porter´s Webiste, specifically, this PDF. Lastly, DipDot´s Youtube channel. He was the main inspiration for this project and his videos are well made.

Parts

162
QtyValueFootprintReferences
59HK19F-DCxxV-SHCRelay_THT:Relay_DPDT_Finder_30.22K1, K2, K10, K11, K12, K13, K14, K15, K16, K17, K18, K19, K20, K21, K22, K23 +43
581N914Diode_THT:D_DO-35_SOD27_P7.62mm_HorizontalD1, D2, D10, D11, D12, D13, D14, D15, D16, D17, D18, D19, D20, D21, D22, D23 +42
21LEDLED_THT:LED_D3.0mmD55, D56, D57, D58, D59, D60, D61, D62, D63, D64, D65, D66, D67, D68, D69, D70 +5
21RResistor_THT:R_Axial_DIN0204_L3.6mm_D1.6mm_P7.62mm_HorizontalR1, R2, R3, R4, R10, R11, R12, R13, R14, R15, R16, R17, R18, R19, R20, R21 +5
1Conn_02x10_Odd_EvenConnector_PinHeader_2.00mm:PinHeader_2x10_P2.00mm_VerticalJ1
1Conn_02x11_Odd_EvenConnector_PinHeader_2.00mm:PinHeader_2x11_P2.00mm_VerticalJ2
1~relaccomp:Conn_RC_Male_100U1

Questions

How big is the Fulladder PCB?

It measures 202.5 × 144.2 mm and has 2 copper layers, 1.6 mm thick.

What parts does the Fulladder use?

162 parts. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.

Where can I download the Fulladder KiCad files?

From the Syntaxer04/RC1Computer repository on GitHub, at the commit this page was made from: the board is Version 0.1/Fulladder/Fulladder.kicad_pcb. PCBKit opens the board in the browser, with nothing to install.

Can I use the Fulladder design in my own project?

Its repository publishes it under the GPL-3.0 licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).

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