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Technical deep dives, programming tricks, ROM lore and other long-form pieces about the ZX Spectrum and how it really works.

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The port that lies about its own number

22 August 2026

Z80 Deep dive ULA Machine code

Every Spectrum program you've ever typed says OUT 254 or IN 254. The ULA doesn't actually check for 254 — it barely checks anything at all. A tiny program proves it, live, on screen.