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Oldskool Concepts

Interactive Lab · ~15 MIN · FREE · LOCAL ONLY

Copper bars, raster splits, palette tricks and sprite multiplexing: effects invented because the hardware left no other option.

Explain where classic hardware tricks came from and why they looked like that.

  • raster beam timing
  • copper bars
  • palette cycling
  • sprite multiplexing
  • hardware as a constraint

Lessons

  1. The beam draws the screen

    Old machines drew one scanline at a time. If you changed a register mid-frame, the change applied only from that line down — which is where most oldskool effects come from.

    TRY THIS BELOW · Move the raster split and watch the upper and lower halves of the frame diverge.

  2. Copper bars

    Changing the background colour on chosen scanlines gives horizontal bands of colour for almost no CPU. Animate the line numbers and the bars appear to move.

    TRY THIS BELOW · Raise the bar count and watch one register write become many horizontal bands.

  3. Palette cycling

    Rotating palette entries animates an image without redrawing a single pixel. Waterfalls and plasma effects were often just a rotating palette.

    TRY THIS BELOW · Give cycling a speed, press Play hardware trick, and watch colour move while the layout stays put.

Raster-trick explorer

Set up a classic oldskool frame: several copper bars, an active raster split and palette cycling, then confirm what you understood.

How many scanline colour changes per frame. Each costs almost no CPU.

The scanline where a register change takes effect — everything below it looks different.

Rotating palette entries animates an image without touching pixels.

Hardware allowed only a few; multiplexing reuses them further down the screen.

Confirm

See what changed

The preview is generated from your choices above.

Conceptual simulation · not hardware emulation

Conceptual raster frame: 0 copper bars, split at line 0 of 200, palette cycle speed 0, 1 sprites per line across 1 reuse band.

WHAT CHANGED · With no copper bars the background is a single colour for the whole frame, because no register changes while the beam travels down the screen. The raster split sits at line 0, so the upper and lower regions are identical. Palette cycling is off, so the image is static even though nothing would need redrawing to animate it. 1 sprite per line stays within a typical hardware limit, so no multiplexing is needed yet.

0/3 REQUIREMENTS MET

  • Bars ≥ 6, split ≥ 60, cycling active
  • Three concepts confirmed
  • Preview changed, or the hardware trick played

COMPLETION RULE · Configure at least six copper bars, an active raster split and palette cycling, and confirm three concepts.

Your plan

Everything above stays on this device. Take a copy with you.

Oldskool Concepts — SceneStart


Checklist:
  [ ] I understand that changes mid-frame apply from that scanline down
  [ ] I understand why copper bars were nearly free
  [ ] I understand palette cycling animates without redrawing
  [ ] I understand sprite multiplexing reuses limited hardware sprites

Completion: 0/3 — Configure at least six copper bars, an active raster split and palette cycling, and confirm three concepts.

SceneStart is not affiliated with any demoparty and cannot certify compliance. The party's published rules always take precedence.

Where to do the real work

  • VICE ↗Free C64 emulator with a debugger that shows raster timing.
  • WinUAE ↗Free Amiga emulator, the usual way to study copper lists.

SCOPE · Nothing here emulates real hardware. The explorer models the ideas so archive footage and source listings start making sense.

FREE FOREVER · A future paid tier could add annotated hardware case studies. The explorer stays free.