The Therac-25 was a computer-controlled radiation therapy machine that occasionally killed the people it was meant to cure. The cause was a race condition — a bug that only triggered when an operator typed too fast — and a company culture that spent two years insisting the machine could not possibly be at fault. It is the case study every software engineer learns from, and it still terrifies them.
Kyle Hill's gripping breakdown of exactly how a few lines of code delivered lethal radiation doses, and how the victims' accounts were repeatedly waved away.
The full anatomy of the machine: a dual-mode linear accelerator that dropped the hardware safety interlocks its predecessors relied on, trusting software instead.
The definitive 1993 paper by the expert witness who reverse-engineered the disaster. Dense, forensic, and the reason the Therac-25 is taught in every safety course.
Hackaday walks engineers through the actual race condition — the 8-second window, the overflowing counter variable — that let the beam fire with no target in place.
Beyond the code: the denials, the missing incident reports, and the corporate refusal to believe patients that turned bugs into body counts.
A modern retrospective on why this decades-old failure still shapes how safety-critical software is written — and why it keeps almost happening again.
A long-form, systems-thinking dissection of how organizational rot — not just a coding slip — made the deaths inevitable. Grim, thorough, occasionally very funny.