vdcmaniac
vdcmaniac v1.0.0 -- title screen

vdcmaniac

2026-08-22
GitHub

A from-scratch Commodore 128 VDC demo showcasing the 80-column chip's rare 64KB-VDC-RAM bitmap modes, from 480x252 colour up to 800x600 monochrome.

A demo for the Commodore 128, compiled with Oscar64, built entirely around the VDC (8563/8568, 80-column chip) rather than the VIC-II. Eight bitmap-mode showcases (VDC-FLI, VDC-HFLI, VDC-IHFLI, VDC-ITFLI, VDC-IMONO, VDC-IM800, VDC Spectrum, plus Plasma and Colour rotation procedural effects), a scripted VDC-SCROLL family panning through bitmaps larger than the display along one or two axes, and a custom raster-IRQ engine driving every effect and the SID soundtrack.

Requirements

  • Krill's fastloader requires exclusive use of the IEC bus. Only one device may be active: the drive holding the demo disk, at device ID 8. Power off or disconnect any other IEC device before running the demo.
  • Only a D81 disk image is supported. Use a real 1581 (or equivalent, e.g. an Ultimate II+) drive.
  • SD2IEC is not supported. Krill's loader needs cycle-exact IEC bus timing that SD2IEC's own IEC emulation does not provide.

Installation

  1. Extract the ZIP -- it contains vdcmaniac.d81 (the disk image) and README.pdf.
  2. Write the D81 to a real 1581 (or equivalent, e.g. an Ultimate II+), or mount it directly on an Ultimate II+ or in VICE.
  3. Boot with only that drive active on the IEC bus, at device 8.

Monitor compatibility varies by VDC mode -- a real-hardware VDC characteristic, not a bug. A Commodore 1901 monitor is confirmed to show every mode correctly, though horizontal/vertical size and centering controls may still need adjusting per mode.

Credits

  • Code: Xander Mol
  • Original inspiration: VDC Mode Mania by Tokra and Mike, Akronyme Analogiker (2012)
  • Raster-sync technique: Peter Hulstede, VDC-Intromaker: Perfektes Rasterzeilen-Timing, 64'er Sonderheft 95
  • Fastloader: Krill's Loader, with TSCrunch compression
  • Compiler: Oscar64 by drmortalwombat
  • Pictures: public-domain paintings/prints and CC-licensed photographs, individually credited in the repository; three ZX Spectrum demoscene graphics credited to their own sceners

Licensed under the GNU General Public License v3.0. Full picture and asset attributions are in the repository's own credit block.

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NameTypeSize
vdcmaniac_v1.0.2.d81D81800.0 KB
vdcmaniac_v1.0.2.zipZIP5.93 MB

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