Racing the ULA: How Programmers Broke the ZX Spectrum's Rules

How did programmers make the ZX Spectrum draw colour it was never meant to hold, and why could the same code freeze on a later model? From border stripes and the floating bus to scanline multicolour, we follow the exact races between the Z80 and ULA that made the tricks work, then show what changed on the +3 and 128K. See a border turn the ULA’s screen fetches blue, Cobra run on a 48K and lock on its first frame on a +3, a 16-column colour band collapse at 17, Dominic Robinson’s 1987 stack routine write two cells at once, and modern Spectrum games and demos carry multicolour across the screen. Our border, floating-bus and multicolour programs from the film, to inspect and run on a Spectrum: https://github.com/retro-computer-tv/... CHAPTERS 0:00 Colour That Should Not Fit 1:24 The Race Begins 2:53 Drawing in the Border 4:49 The Port Nobody Answers 6:57 Ten Bytes Freeze Cobra 12:58 One Line Before the Next 16:53 Two Cells at a Time 19:14 Making Time for a Game 22:45 Why 70,908? SELECTED SOURCES • 48K ZX Spectrum Technical Information • 128K ZX Spectrum Technical Information • StarTip1.txt (spectrumcomputing.co.uk, PDF) • BIFROSTENGINEV1.2.txt (spectrumcomputing.co.uk, PDF) • GitHub - Paulie68000/ZXSpectrumCobra: Full reverse engineered source code of Jonathan "Joffa" Smith's Cobra • The Definitive Programmer’s Guide to Using the Floating Bus Trick on the ZX Spectrum • In Color by Darklite & Offence (pouët.net) All 33 sources, and credits for every image, clip and track: https://curio-tv.com/credits/racing-t... MUSIC "Beside Me" by Patrick Patrikios (YouTube Audio Library) https://support.google.com/youtube/an... "Between The Spaces" by The Soundlings (YouTube Audio Library) https://support.google.com/youtube/an... "Denied Access" by Density & Time (YouTube Audio Library) https://support.google.com/youtube/an... "Galactic Bass" by John Patitucci (YouTube Audio Library) https://support.google.com/youtube/an... "To Have to in Least Water", "Run Letting" by pATCHES, licensed under YouTube Audio Library https://support.google.com/youtube/an... "Lifelong" by Anno Domini Beats (YouTube Audio Library) https://support.google.com/youtube/an... "Loading Screen" by Dyalla (YouTube Audio Library) https://support.google.com/youtube/an... "Peaceful Mind" by Astron (YouTube Audio Library) https://support.google.com/youtube/an... "Sun Awakening" by Futuremono (YouTube Audio Library) https://support.google.com/youtube/an...