HN
Today

DCJ11Hack+ – DEC PDP/11 based homebrew computer

Paula Maddox shares DCJ11Hack+, her meticulously crafted homebrew computer project centered around the iconic DEC DCJ11 processor. This detailed hardware build features custom PCB designs, memory maps, and assembly code examples for a truly hands-on retrocomputing experience. HN loves these passion projects that revive vintage technology with modern hobbyist ingenuity, offering a deep dive into computer architecture.

11
Score
0
Comments
#14
Highest Rank
4h
on Front Page
First Seen
Apr 3, 10:00 PM
Last Seen
Apr 4, 1:00 AM
Rank Over Time
14212830

The Lowdown

TechPaula presents DCJ11Hack+, a personal endeavor to construct a homebrew computer system built around the iconic DEC DCJ11 CPU. Inspired by existing PDP-11 hack projects, Maddox has designed a modular system that allows for functionality expansion via a backplane, driven by a deep appreciation for the chip's design. This project is a comprehensive guide for anyone looking to delve into classic computer hardware.

  • The project provides schematics and PCB files (created in KiCAD) for a main CPU board, along with RAM, ROM, and text display boards, including necessary PAL files for programmable logic.
  • Displays include both character-based text output and a 16x16 dot matrix LED panel, showcasing basic visual capabilities controlled via memory-mapped I/O.
  • A detailed memory map outlines the allocation of 32KB RAM, 16KB ROM, and specific ranges for the text and matrix displays, available in both hexadecimal and octal.
  • The system powers up into an "ODT" (Octal Debugging Technique) mode, facilitating interactive experimentation and understanding of the DCJ11 chip's operation.
  • Example assembly code is provided, ranging from a basic "Hello World!" to animated patterns like "Knight Rider," with guidance on using a PDP-11 simulator for development.
  • A notable design decision simplifies circuitry by exclusively supporting 16-bit word-wide memory operations, with a caveat that byte commands could lead to data corruption.
  • The project is openly shared on Codeberg, reflecting its status as a hobbyist's ongoing passion project, with future updates planned as time permits.

DCJ11Hack+ stands as a testament to the enduring appeal of vintage hardware and the dedication of hobbyists to meticulously recreate and understand classic computer architectures, offering a comprehensive resource for anyone interested in building their own PDP-11-inspired machine.