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Y Ddraig: A Motorola 68000 retro computer.

Y Ddraig: A 68000 computer

Y Ddraig (Welsh for The Dragon) is a custom-built computer based on the Motorola 68000 processor. The name was chosen because originally I considered calling it Dragon, but I wanted something distinctly Welsh while also avoiding confusion with Dragon Data’s Dragon 32/64 computers, another Welsh computer system that used the Motorla 6809.

As a long-time Amiga user, I had been considering designing my own 68000-based computer for quite a while. The earliest inspiration for this design came from the excellent Kiwi, a 68008-based design by Simon Ferber. What began as a simple “full 68000” version of the Kiwi has since evolved into the current design. The initial design for Y Ddraig was originally conceived as a single-board computer, after looking at various graphics and sound options and wanting to try several different options, I decided to for for a more modular system with expansion slots, giving me the freedom to experiment with custom hardware and configurations.

Hardware #

One of the core goals behind Y Ddraig is to recapture the feel of classic home computers: when powered on, it immediately boots into a built-in operating system stored in ROM.

The system currently features:

  • Motorola 68000 CPU at 10 MHz
  • 512 KB ROM for the operating system
  • 1 MB of static RAM (expandable with up to 8 MB of DRAM)
  • Two RS-232 serial ports
  • Parallel port for printers or peripherals
  • Real-time clock
  • PS/2 keyboard and mouse ports
  • IDE hard drive interface
  • Four expansion slots, each supporting 256-byte register access or 1 MB direct memory access

Operating System #

On startup, Y Ddraig boots into DdraigDOS, a lightweight disk operating system. It uses the FatFS library to support FAT-formatted hard drives. Users can interact through either a serial terminal or directly via keyboard and display (with a video expansion card).

DdraigDOS includes a set of built-in commands and can also load and execute programs in ELF format from the hard drive. Software and data can be transferred over the serial port, which is especially useful during development.

Software Development #

Software for Y Ddraig is cross-compiled using GCC, with a custom Newlib providing system calls into the operating system. A dedicated hardware-access library is also in development, designed to simplify programming without requiring direct hardware manipulation.

A built-in BASIC interpreter, the late Lee Davidson’s 68000 EhBASIC, provides an immediate programming environment built into the ROM, much like classic home computers. Longer-term plans include adding a text editor, assembler, and compiler, allowing software to be developed entirely on the machine without relying on cross-compilation.

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