Galaksija is a small home microcomputer designed in 1983 in Belgrade by Voja Antonić. Meant as a DIY computer it was later also manufactured on production lines and was the most popular domestic home computer. Original circuit is based on a Zilog Z80 microprocessor and requires no application-specific integrated circuits, implementing the digital circuit with general purpose discreet logic chips.

For anyone wanting to build a Galaksija today the original design has a number of problems. It's based on obsolete 74LS logic, which is hard to buy these days. The circuit also depends on a few unspecified signal timing details of the Z80 microprocessor, meaning that it will not work with all Z80 CPUs you can get today.

This page contains information about CMOS Galaksija, my remake of the original circuit using modern 74HC-series chips. It also fixes the Z80 timing issues (at the cost of one additional integrated circuit) and adds a composite video output that is compatible with modern TVs.

Hardware design

Please see this directory for the latest version of design documents.

The incomplete Galaksija ROM disassembly

This is an assembly source file automatically generated from binary ROM image with z80dasm. Human-readable comments were gradually added later by me while working on CMOS Galaksija (with the wonderful Incomplete Spectrum ROM Assembly as a style guide).

This source can be assembled into a binary identical to the original ROM image with a Z80 assembler like z80asm.

Read assembly file online

Further information

CMOS replica is described in detail in my diploma thesis (Slovene language).

Over the years I have also published many English blog posts that describe intimate details of Galaksija's circuit.

If you want to develop software for Galaksija on a modern computer, my development tools are useful. There is also a Galaksija port of the z88dk.

Galaksija resources elsewhere on the web:

• Collection of original software
• Old magazine scans
• Galaksija.org forum

Other Galaksija remakes:

• µGalaksija, a FPGA implementation.
• Galaksija GAL, a PLD implementation.

Galaksija emulators:

• GalaxyWin, for Microsoft Windows.
• Galaxy, for DOS.
• Galaksija for Sinclair ZX Spectrum 128k
• Galaksija Emulator for SAM Coupé