Fanless MacBook Air Caused 54% Benchmark Error Due to Thermal Throttling

A developer benchmarking a search engine's multi-thread performance on an Apple M4 MacBook Air discovered that thermal throttling silently corrupted an entire dataset. Because the fanless laptop heats up under sustained load, running tests sequentially from 1 to 11 threads meant later thread counts always executed on a hotter, slower chip — a systematic bias, not random noise. A result showing 11 threads completing in 5.2 seconds turned out to be a one-off cold-chip reading, later reproducing at 8.0 seconds under warmer conditions. The developer resolved the issue by switching to a round-robin measurement protocol — cycling through all thread counts across multiple full sweeps and taking the per-thread median — which fairly distributed thermal states across every configuration. The corrected 128-measurement run produced a reproducible performance plateau at 8 threads with a 3.0x speedup, and the anomalous record disappeared entirely.