What happens when

You press the power button

A short press that looks trivial hides a careful dance between the power management chip, the processor and every subsystem attached to it.

Following the request, step by step

Scroll through. Each step is something that genuinely happens, with the time it typically takes.

Step 01<5 ms
The button is debounced
The power management chip confirms a real press.
Mechanical switches produce several rapid electrical transitions for one press. The power management integrated circuit filters those into a single clean event so the system does not wake repeatedly.
Step 0210–30 ms
The main processor wakes
The SoC leaves its deepest sleep state.
Phones spend most of their life in states where most of the chip is unpowered. Waking requires restoring clock domains, re-enabling power rails and bringing up memory in the right sequence.
Step 0320–60 ms
The display powers up
Panel rails settle and the first frame is pushed.
An OLED panel needs its supply rails to stabilise before it can show anything. Meanwhile the display controller is already receiving a framebuffer, so as soon as the panel is ready there is content to show.
Step 0430–80 ms
State is restored
The lock screen renders from saved state.
The system does not boot from scratch. It resumes the suspended state of the running system, which is why unlocking a modern phone feels instantaneous compared with older devices that truly powered down.
Step 05100 ms – 2 s
Radios re-sync
Cellular and Wi-Fi reconnect in parallel.
The radios were also asleep. They re-register with the network and re-associate with known access points. This is why notifications can arrive a moment after the screen comes on rather than before it.

The same sequence as a diagram you can play and step through.

Step 1/4tilt detected

An always-on sensor detects a change — motion, light, a tap — without waking the main processor.

Part inspector

Select any part of the diagram to read what it does. Play the sequence, or step through it yourself.

Follow a single request from your keyboard to a server on another continent and back again, in the time it takes to blink.

From a tap on glass to a finished JPEG in under a second, a chain of hardware and software decisions is made.