Overview
- Software engineer Sam Henri Gold compared iOS 4.0 and 4.0.1 and identified a 20-byte change to a lookup table in the CommCenter binary.
- The revised thresholds mapped dBm to bars less optimistically, curbing dramatic swings from five bars to two during the so-called death grip.
- Apple had already acknowledged its bar formula overstated signal and released iOS 4.0.1 with a recalibration guided by AT&T.
- Gold also noted Apple increased the visual height of low bars in 4.0.1, a user‑interface tweak that reduced alarm over weak signal states.
- The technical clarification aligns with Apple’s broader response at the time, including free Bumper cases, an antenna redesign in the iPhone 4S, and roughly $175 million reserved for related costs.