Skip to the content
PCBKitNew board
2 layers101.6 × 55.9 mmClock, the printed circuit board in 3D

Modular 8-bit computer built with TTL logic units to create a "Simple as Possible" system

Size
101.6 × 55.9 mm
Copper layers
2
Thickness
1.6 mm
Parts
72
Nets
102
Pads
353
Tracks, vias
1,151, 78
Pours
2
Routed
Yes
KiCad
KiCad 6 (file 20211014)
Created
14 Jan 2025
Updated
26 Jan 2025

Overview

Clock is an open-source printed circuit board by ifilot, from the ifilot/sap-smd repository on GitHub, published under the CERN-OHL-S-2.0 licence. It is a 2-layer board of 101.6 × 55.9 mm with 72 parts on 102 nets, routed with 1,151 tracks and 78 vias.

It is built around the 74HC00D, 74HC193D and 74HC02, with the 74HC14, 74HC151D and SWS1 among its other parts. Its parts include 20 capacitors, 13 resistors, 12 ICs, 11 diodes and 8 switches. It belongs with the retro computing and games and lEDs and displays boards of this library.

Main components

6

README

README.md

Modular 8-bit "Simple as Possible" TTL-Logics Computer

Work in Progress CERN-OHL

This project showcases the design and construction of a modular 8-bit computer built with TTL logic units. The core principle behind the project is to create a "Simple as Possible" system, focusing on simplicity, modularity, and compactness.

SAP-SMD demo

Key Features

  • TTL Logic-Based Design: The computer is built using traditional TTL (Transistor-Transistor Logic) components, adhering to a fundamental, hands-on approach to computing.
  • Modular Architecture: Designed for modularity, each functional unit (ALU, registers, memory, control logic, etc.) is implemented as a separate module, allowing for easy debugging, customization, and scalability.
  • Compact Form Factor: By predominantly using SMD (Surface-Mount Device) components, the overall size of the computer is significantly reduced compared to traditional through-hole designs, making it more efficient and portable.
  • Educational Value: Serves as an excellent learning resource for understanding the basic principles of digital logic, computer architecture, and how these concepts come together to form a functional computing system.
  • Customization Potential: The modular approach allows users to experiment with different configurations and expand the system to suit specific needs or projects.

Technical specifications

  • 8 bit program counter
  • 256 bytes of RAM and 256 bytes of program ROM
  • 256 configurable programs via a dip switch
  • Three general-purpose register: A, B and T
  • Simple ALU allowing for addition and subtraction
  • EEPROM-configurable instruction decoder
  • Custom assembly language including Python-based assembler

Goals of the Project

The project aims to:

  1. Simplify Complexity: Break down the workings of a computer into comprehensible modules without unnecessary abstraction.
  2. Promote Learning: Provide an accessible platform for enthusiasts, educators, and students to explore computer design.
  3. Encourage Miniaturization: Demonstrate how SMD components can be used effectively in hobbyist and educational projects to save space while maintaining functionality.

Why SMD Components?

SMD components offer several advantages:

  • Space Efficiency: Significantly smaller than through-hole components, enabling more compact designs.
  • Modern Availability: Easier to source and more reflective of contemporary electronics practices.
  • Scalability: Allows for a more complex system without requiring excessive physical space.

Who Is This For?

This project is ideal for:

  • Hobbyists and Makers interested in retrocomputing and hardware design.
  • Students and Educators looking for hands-on experience with digital logic and computing fundamentals.
  • Researchers and Enthusiasts exploring minimalist computing and modular design approaches.

Getting Started

  1. Clone the Repository: Download the files and schematics from this repository.
  2. Review the Documentation: Detailed explanations and schematics for each module are available in the docs directory.
  3. Assemble and Test: Follow the provided instructions to assemble and test the modules step-by-step.
  4. Customize: Modify or expand the design to suit your needs or explore specific areas of interest.

Contributing

Contributions to this project are welcome! If you have ideas for improvements, additional features, or alternative designs, feel free to fork the repository and submit a pull request.

Parts

72
QtyValueFootprintReferences
150.1uFCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC3, C7, C8, C9, C10, C11, C12, C13, C14, C15, C16, C17, C18, C19, C20
610kResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR1, R4, R5, R6, R10, R11
4330Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR7, R9, R12, R13
474HC00Package_SO:SO-14_3.9x8.65mm_P1.27mmU2, U5, U8, U11
374HC193Package_SO:SO-16_3.9x9.9mm_P1.27mmU7, U10, U12
20.01uFCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC1, C6
210kResistor_SMD:R_Array_Convex_4x0603RN1, RN3
21kResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR2, R3
2220Resistor_SMD:R_Array_Convex_4x0603RN2, RN4
2SE555Package_SO:SOIC-8_3.9x4.9mm_P1.27mmU1, U9
1.1uFCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC4
115pFCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC2
11MResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR8
11MPotentiometer_THT:Potentiometer_ACP_CA9-V10_VerticalRV1
11uFCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC5
174HC02Package_SO:SO-14_3.9x8.65mm_P1.27mmU6
174HC14Package_SO:SO-14_3.9x8.65mm_P1.27mmU3
174HC151Package_SO:SO-16_3.9x9.9mm_P1.27mmU4
1CD0LED_SMD:LED_0805_2012Metric_Pad1.15x1.40mm_HandSolderD6
1CD1LED_SMD:LED_0805_2012Metric_Pad1.15x1.40mm_HandSolderD7
1CD2LED_SMD:LED_0805_2012Metric_Pad1.15x1.40mm_HandSolderD8
1CD3LED_SMD:LED_0805_2012Metric_Pad1.15x1.40mm_HandSolderD9
1CLEARButton_Switch_THT:SW_PUSH_6mmSW7
1CLKLED_SMD:LED_0805_2012Metric_Pad1.15x1.40mm_HandSolderD1
1Clock DividerButton_Switch_SMD:SW_DIP_SPSTx04_Slide_6.7x11.72mm_W8.61mm_P2.54mm_LowProfileSW2
1HALTLED_SMD:LED_0805_2012Metric_Pad1.15x1.40mm_HandSolderD11
1MANCLKButton_Switch_THT:SW_PUSH-12mm_Wuerth-430476085716SW4
1MANHALTcustom_tactile_button:tactile_buttonSW8
1MANHALTLED_SMD:LED_0805_2012Metric_Pad1.15x1.40mm_HandSolderD10
1Reset CounterButton_Switch_SMD:SW_DIP_SPSTx04_Slide_6.7x11.72mm_W8.61mm_P2.54mm_LowProfileSW6
1S0LED_SMD:LED_0805_2012Metric_Pad1.15x1.40mm_HandSolderD2
1S1LED_SMD:LED_0805_2012Metric_Pad1.15x1.40mm_HandSolderD3
1S2LED_SMD:LED_0805_2012Metric_Pad1.15x1.40mm_HandSolderD4
1SIGNALSConnector_PinHeader_2.54mm:PinHeader_1x10_P2.54mm_VerticalJ1
1SWS0Button_Switch_THT:SW_PUSH_6mmSW1
1SWS1Button_Switch_THT:SW_PUSH_6mmSW3
1SWS2Button_Switch_THT:SW_PUSH_6mmSW5
1TCXO-14Oscillator:Oscillator_DIP-14X1
1XConnector_PinHeader_2.54mm:PinHeader_1x10_P2.54mm_VerticalJ2
1~{CLR}LED_SMD:LED_0805_2012Metric_Pad1.15x1.40mm_HandSolderD5

Questions

How big is the Clock PCB?

It measures 101.6 × 55.9 mm and has 2 copper layers, 1.6 mm thick.

What parts does the Clock use?

72 parts, built around the 74HC00D, 74HC193D, 74HC02 and 74HC14. 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 Clock KiCad files?

From the ifilot/sap-smd repository on GitHub, at the commit this page was made from: the board is pcb/components/clock/clock.kicad_pcb and its schematic pcb/backplates/bp-leanplate/bp-leanplate.kicad_sch. PCBKit opens the board in the browser, with nothing to install.

Can I use the Clock design in my own project?

Its repository publishes it under the CERN-OHL-S-2.0 licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).

More from ifilot/sap-smd

10
  • 2 layers101.6 × 55.9 mmInstruction decoder, the printed circuit board in 3D

    Instruction decoder

    ifilot/sap-smd

    Modular 8-bit computer built with TTL logic units to create a "Simple as Possible" system

    68 parts2CERN-OHL-S-2.0
  • 2 layers101.6 × 55.9 mmAlu advanced, the printed circuit board in 3D

    Alu advanced

    ifilot/sap-smd

    Modular 8-bit computer built with TTL logic units to create a "Simple as Possible" system

    51 parts2CERN-OHL-S-2.0
  • 2 layers101.6 × 55.9 mmRamrom, the printed circuit board in 3D

    Ramrom

    ifilot/sap-smd

    Modular 8-bit computer built with TTL logic units to create a "Simple as Possible" system

    48 parts2CERN-OHL-S-2.0
  • 2 layers101.6 × 55.9 mmAlu, the printed circuit board in 3D

    Alu

    ifilot/sap-smd

    Modular 8-bit computer built with TTL logic units to create a "Simple as Possible" system

    42 parts2CERN-OHL-S-2.0
  • 2 layers101.6 × 55.9 mmOutput register, the printed circuit board in 3D

    Output register

    ifilot/sap-smd

    Modular 8-bit computer built with TTL logic units to create a "Simple as Possible" system

    30 parts2CERN-OHL-S-2.0
  • 2 layers319.9 × 154.4 mmBp leanplate, the printed circuit board in 3D

    Bp leanplate

    ifilot/sap-smd

    Modular 8-bit computer built with TTL logic units to create a "Simple as Possible" system

    29 parts2CERN-OHL-S-2.0
  • 2 layers101.6 × 27.9 mmProgram counter, the printed circuit board in 3D

    Program counter

    ifilot/sap-smd

    Modular 8-bit computer built with TTL logic units to create a "Simple as Possible" system

    26 parts2CERN-OHL-S-2.0
  • 2 layers101.6 × 27.9 mmGeneral purpose registers, the printed circuit board in 3D

    General purpose registers

    ifilot/sap-smd

    Modular 8-bit computer built with TTL logic units to create a "Simple as Possible" system

    23 parts2CERN-OHL-S-2.0
  • 2 layers48.3 × 27.9 mmBusreader, the printed circuit board in 3D

    Busreader

    ifilot/sap-smd

    Modular 8-bit computer built with TTL logic units to create a "Simple as Possible" system

    16 parts2CERN-OHL-S-2.0
  • 2 layers101.6 × 55.9 mmLcd display, the printed circuit board in 3D

    Lcd display

    ifilot/sap-smd

    Modular 8-bit computer built with TTL logic units to create a "Simple as Possible" system

    12 parts2CERN-OHL-S-2.0

Similar boards

  • 2 layers100 × 100 mmPortcard RevC, the printed circuit board in 3D

    Portcard RevC

    retrac0/retelex

    Retro telephone exchange. Also retro telex exchange.

    75 parts
  • 2 layers178 × 711 mmMSAP-2 rev.A SMD, the printed circuit board in 3D

    MSAP-2 rev.A SMD

    mehrantsi/MSAP-2

    An 8-bit computer. Successor to MSAP-1

    658 parts13MIT
  • 2 layers245.1 × 160 mm8-Bit CPU 32k, the printed circuit board in 3D

    8-Bit CPU 32k

    slu4coder/Minimal-64x4-Home-Computer

    My DIY TTL home computer with VGA and PS/2 and 4x the processing power of a Commodore C64 or Apple II.

    139 parts326
  • 2 layers191.8 × 121.3 mm8-Bit CPU 32k, the printed circuit board in 3D

    8-Bit CPU 32k

    slu4coder/Minimal-UART-Computer-1-2

    Legacy: Version 1 and 2 of my TTL-only CPU featuring UART I/O, an expansion port, 512KB SSD at up to 10MHz clock speed

    109 parts184
  • 2 layers212 × 126 mmUno-14500, the printed circuit board in 3D

    Uno-14500

    juniperlynx/Uno-14500

    A trainer / demonstration system for the Motorola MC14500B

    84 parts1
  • 2 layers180.3 × 112.4 mm8-Bit CPU 32k, the printed circuit board in 3D

    8-Bit CPU 32k

    slowcorners/Minimal-UART-CPU-Dev

    89 parts
  • 2 layers100 × 100 mmHC4 KiCad, the printed circuit board in 3D

    HC4 KiCad

    nasu8151/HC4

    Schematics and board of HC4 E (E means "for Education").

    175 parts8