The No-CPU Amiga Demo Challenge

Summary

The No-CPU Amiga Demo Challenge This is an open challenge to create demos that run entirely on the Amiga custom chips without involving the CPU. This repository contains the rules of the challenge and a runner application for launching no-CPU demos. This is intended as a standard specification of the no-CPU platform for demo competitions. There will be a dedicated no-CPU Amiga demo competition at Gerp 2026, January 23-25, 2026. In addition, this is an ongoing challenge — an invitation to explore a different kind of demo platform. An invitation demo — itself a no-CPU demo — was released at Evoke 2025. The full source code for the demo is available here. Whenever you release a no-CPU demo, you are encouraged to write a comment about it on the demo announcement issue. There's also a FAQ. Background The Amiga custom chips (affectionately named Alice, Lisa and Paula in the AGA version of the chipset) were remarkably powerful for their time, enabling the Amiga computers — with their modestly-powered CPUs — to perform graphical and musical feats that required heavy computation on most contemporary platforms. This challenge aims to discover just how powerful these chips really are by exploring what they can do completely on their own, without the CPU even telling them what to do. There have been several demo competitions in the past with a technical theme. Examples include Atari zero bitplane, Atari mixed-resolution, C64 only sprites and C64 border only. This is a similar idea for the Amiga — no CPU, custom chips only. Technical details A no-CPU demo takes the form of a raw memory image that specifies the initial contents of chip memory. Together with the initial state of the hardware registers (specified below) this memory image fully defines the demo. The memory image is loaded into memory by a runner application, which serves as the demo executable. You can use the runner as is or modify it to your liking, but in order to qualify as a no-CPU demo according to this challe...