What is the infant-mortality region of the bathtub curve?	The early high-failure-rate period caused by latent defects — marginal solder joints, microscopic voids, contaminated interfaces — that were not caught by probe test.
At what temperature does burn-in operate?	Typically 125°C, combined with elevated voltage.
How long does a typical burn-in recipe run?	48 to 168 hours — two to seven days.
What happens to chips that fail during burn-in?	They are caught and discarded; surviving chips are past the infant-mortality phase and are the ones that ship.
What does HTOL stand for and what does it validate?	High Temperature Operating Life — it validates the long-term behavior of the chip <em>design</em> (not individual units) by operating a sample population at elevated stress for 1,000+ hours and extrapolating using the Arrhenius equation.
What reliability target does the chapter cite for AI cluster chips?	Fewer than 1 failure per billion device-hours — less than 1 FIT.
What does RAS stand for?	Reliability, Availability, and Serviceability.
Name four things the RAS engine monitors.	ECC errors in HBM, voltage droop on power rails, junction temperatures across the die, and crossbar errors in NVLink (also: bit-flip patterns from cosmic-ray soft errors).
What can the RAS engine do with a single bad core?	Mark it as bad and exclude it from scheduling without bringing the rest of the chip down.
How long is a shipped Rubin GPU expected to run at design limits?	Four to six years, twenty-four hours a day, seven days a week.