Docs / Graphics and display

Inactive GPU powers down correctly

graphics.power-downAutomaticMedium confidence

How it tests

On Macs with two GPUs, picks the one not marked as the boot VGA device and watches its runtime power state for 12 s.

How it decides

Supported when it reads “suspended” within 12 s. Failed when it stays active or has no runtime power state.

How sure it is

Runtime PM state is the right signal, but 12 s right after the GPU test may be too short, and “suspended” in sysfs doesn't prove the hardware is switched off.

What could mislead it

  • Could fail when it shouldn'tThe GPU was just used by the graphics probe and its autosuspend delay is longer than 12 s.
  • Could fail when it shouldn'tThe live image leaves runtime PM on “on” where an installed system (or a later udev rule) sets “auto”. The evidence names the control setting.
  • Could pass when it shouldn'tRuntime PM says suspended but gmux still powers the GPU.
  • Could fail when it shouldn'tThe boot VGA guess picks the wrong GPU on a gmux Mac.