Advanced Patterns
Expert-level patterns pushing hardware to its limits
Commodore 64
2 patternsSID Multi-Voice
Step a note pattern once per raster interrupt, handing each of the SID's three voices its note from a frequency table — the skeleton of every C64 music player.
Sprite Multiplexing
Reuse the C64's eight hardware sprites several times down the screen to show sixteen, twenty-four or more — the raster trick behind every busy C64 game.
Sinclair ZX Spectrum
2 patternsAY Music
Step a note pattern once per interrupt, handing each of the AY's three channels its note from a period table — a full three-voice tune that plays in the background while the game runs.
Masked Sprites
The Spectrum has no hardware sprites, so a moving object is drawn by hand — AND a mask to punch a hole in the background, OR the image into it — with pre-shifted copies for pixel-accurate, fast movement.
Nintendo Entertainment System
3 patternsA Music Engine
Step a note pattern once per frame from the NMI, handing each APU channel its note from a timer table — the skeleton of every NES music driver.
Feeding New Columns
As the NES scrolls sideways, write a fresh column of tiles into the offscreen nametable each time the view crosses a tile boundary — so a level far wider than two screens rolls past seamlessly.
Sprite 0 Split
Keep a status bar fixed at the top of the screen while the playfield below scrolls — by placing sprite 0 at the boundary and changing the scroll the instant its hit flag fires. The NES's answer to the mid-screen split.
Commodore Amiga
4 patternsFour-Channel Music
Drive all four of Paula's channels from a note sequence, stepping the pattern on a timer interrupt and turning note numbers into periods — the skeleton of every Amiga tracker and MOD player.
Blitter Line Draw
The blitter isn't only a copier — in line mode it plots a Bresenham line in hardware, one pixel at a time, straight into a bitplane. Feed it endpoints and an octant; it draws the line while the CPU moves on.
Cookie-Cut Blit
Draw a shaped, transparent object over the background using all four blitter channels — a mask decides pixel by pixel whether to keep the image or the scenery behind it. The heart of every Amiga bob.
Copper Split Screen
Have the copper reprogram the bitplane pointers part-way down the frame so the top and bottom of the screen show different bitmaps — a scrolling playfield above a rock-steady status panel, beam-locked and free.