Building a macOS app to know when my Mac is thermal throttling

Original Article ↗ Hacker News Discussion ↗

Usefulness of a thermal‑throttling indicator

  • Some see clear value: it reveals when a runaway or badly written process is heating the machine so they can kill it before the battery drains or performance tanks.
  • Especially useful on fanless Macs (e.g., MacBook Air) where there is no audible cue that the system is under heavy thermal load.
  • Others question its practical utility: once you know you’re throttling, options to fix it on Apple Silicon are limited.

What users can do about throttling

  • Software side: quit background apps, stuck loops, or misbehaving processes; take a break while the machine cools.
  • Hardware/usage side: improve airflow (elevate laptop, external fan, avoid insulating surfaces), move to a cooler room, or adjust fan curves on models with fans using tools like iStat Menus, Mac Fan Control, TG Pro, etc.
  • Apple’s “High Power Mode” on some Apple Silicon Pros lets fans run harder at the cost of noise.

Fan control: curves vs PID and hardware longevity

  • Debate over simple temperature→fan-speed curves vs PID-style control aiming for a fixed temperature.
  • Several argue PID is overkill for consumer laptops: there’s no “too cold”, just “not too hot + low noise”, so a curve is simpler and “good enough”.
  • Others recall “conventional wisdom” that minimizing thermal cycling (temperature swings) can improve hardware longevity, which PID might help with, but this is not universally prioritized in consumer gear.
  • Commenters note PID-like schemes appear mostly in high‑reliability equipment that can also heat as well as cool.

Apple thermal design, Intel vs Apple Silicon

  • Many recount severe throttling on Intel MacBook Pros (especially 2016–2019 and i9 variants), sometimes mitigated by:
    • Forcing max fans, external cooling pads/fans, disabling Turbo/HT, or even charging from specific USB‑C ports.
  • Multiple reports that simply charging from the “wrong” side on the 2019 i9 caused massive kernel_task load and throttling; charging from the other side largely fixed it.
  • Apple Silicon machines are widely described as dramatically better: much quieter, cooler, and less prone to throttling at similar power draws.

Implementation details and ecosystem

  • macOS thermal pressure APIs via ProcessInfo appear buggy for some; using thermald notifications works more reliably.
  • Alternative tools mentioned include Stats, Hot, Macs Fan Control, and others; several want the new app in Homebrew and/or the Mac App Store.
  • Some hope Apple will integrate a built‑in indicator into macOS; others even suggest a hardware LED, though many doubt Apple would expose such a signal for mainstream users.