C64 Uber Sound Solution

A PAL-timed Commodore 64 demo that combines a multicolour bitmap presentation, a split-raster sine scroller, animated star sprites, and a three-voice SID acid music engine. The source is written in 6502 assembly and builds with ACME.

Copyright (C) 2026 Ulf Bertilsson. Licensed under the GNU General Public License v3.0 only; see NOTICE.

Live VICE captures

Every image below is an unedited VICE framebuffer from the assembled PRG. The demo changes on every music tick, so the frames show separate moments in one continuous run rather than static artwork or mockups.

Main bitmap and scroller scene

The bitmap logo, upper sprite field, black border, and lower sine scroller are all active at once.

Later music and scroller phase

This capture shows the later colour and scroller position reached after the SID pattern player has continued through the sequence.

Alternate sprite and scroller state

The beat-driven sprite positions and lower message continue to evolve while the bitmap stays in its black-border presentation.

Features

• Bitmap top section: uploads an 8,000-byte bitmap, screen, colour, and custom character set into the C64 memory layout at startup.
• Two-stage raster IRQ: a top interrupt selects the bitmap presentation; a split at raster line 200 switches to the bottom text/scroller area.
• Black-border visual discipline: beat reactions alter bitmap and sprite colours while retaining a black border and background.
• Animated sprite field: four hardware sprites use beat-driven position, colour, and X/Y expansion changes.
• Three-voice SID player: bass pulse, acid lead/arp, and noise percussion share an LP/BP filter with a step-driven cutoff LFO.
• Fine scroller: a repeating 32-character message moves across the lower screen with a beat-aware sine lift.
• Data integrity: source checks validate branch spans, label uniqueness, table sizes, and asset layout before the strict ACME build.

Quick start

Download uber_sound_solution.prg from the latest release, then run it in a PAL-capable C64 emulator or on suitable hardware. With VICE:

x64sc -autostartprgmode 1 -autostart uber_sound_solution.prg

The PRG has a BASIC loader that starts SYS 4096 automatically. It runs until the machine is reset. The demo targets PAL timing and is tuned for a MOS 8580- style SID; NTSC and alternate SID revisions are not currently validated.

Build from source

Requirements:

• ACME 0.97 or newer;
• Python 3;
• VICE x64sc or x64 to run the demo.

git clone https://github.com/djayuffe/C64-Uber-Sound-Solution.git
cd C64-Uber-Sound-Solution
make
./vice_run.sh build/uber_sound_solution.prg

make runs the static checks first, then uses ACME --strict-segments to produce build/uber_sound_solution.prg. ./make.sh is a small wrapper around the same Makefile for environments that prefer a shell entry point.

Architecture

Area	Details
Entry	BASIC 10 SYS4096 transfers control to Start at $1000.
Video	Bank 0; bitmap at $2000, bitmap screen at $0400, text charset at $0800.
IRQs	IrqTop drives the bitmap/SID/effects work; IrqSplit selects text mode and advances the scroller.
Assets	Four release assets load from $6000; source guards against growth into $a000.
Audio	SID voices 1–3 supply bass, lead, and percussion through the shared filter.

The full routine, asset, and release-maintenance discussion is in docs/DEVELOPMENT.md. The current source and cleanup audit is recorded in AUDIT.md.

Verify and release

make clean
make
shasum -a 256 -c SHA256SUMS.txt

SHA256SUMS.txt covers every tracked release file except itself. GitHub Actions runs the same clean build, shell-script validation, and checksum verification for pull requests, pushes, version tags, and published releases; successful workflows retain the PRG as a downloadable artifact.

Repository layout

• src/uber_intro.asm — the single authoritative 6502 source file.
• assets/ — bitmap, screen, colour, charset, and three direct VICE frames.
• source_music/ — human-readable source material for the composition.
• tools/ — focused static integrity checks used by make verify.
• docs/DEVELOPMENT.md — build, runtime contract, CI, and release guide.
• CHANGELOG.md — versioned release notes.
• LICENSE and NOTICE — GPLv3 terms and Ulf Bertilsson attribution.

License

All original code, documentation, and bundled runtime assets are Copyright (C) 2026 Ulf Bertilsson and released under GPL-3.0-only. You may copy, modify, and redistribute the project under GPLv3; derivatives must retain the required license notices. The project is provided without warranty.