How long do you need to hold down the power button to turn off a PC? | Hacker News Reader

How long do you need to hold down the power button to turn off a PC?

osnews.com

59 pointsArodex20 comments

Could the confusion be that the 12 seconds only apply when the OS fails to respond to the power-down request? I recall struggling with laptops stuck in a boot loop, and it did pay off to hold the power-down button a little longer.

My desktop, which has an Asus motherboard but doesn't have Windows installed on it, also takes in the 3-4 seconds range for a hard shutdown. I would have assumed that it is entirely hardware-dependent and the OS hasn't much to do with it. On my Macbook Air I just counted 5 for a hard shutdown.

Looks like Microsoft forgot to talk to hardware manufacturers about this feature...

The cool thing is my office Microsoft Surface Laptop that will randomly wake up and sit there with its keyboard backlight full on and act dead... then you have to hold it for 30 seconds!

I guess I'm the one contributing to those crashlogs.

But that doesn't explain where the dumps are coming from.

> What further complicates matters is that Chen details how the kernel dumps created after pressing the power button for 8 seconds do, in fact, get sent to Microsoft once the computer turns on again. In fact, he is one of the people who gets to see these dumps and respond to them, so obviously they are indeed rolling in.

Appropriately for halloween, this seems somewhat spooky.

I guess that many PCs don't generate the dumps because they shut down after a shorter period, and they're just analyzing kernel dumps from a subset of PCs.

Right, but that means there must be some PCs that take > 8 seconds. Has... anyone ever seen one? In the past two decades? (I'm time bounding the question only because I know nascent PCs did lots of weird stuff.)

It's not like there are that many PC SKUs out there (or motherboard SKUs for custom stuff). And even if there are two weird models, how useful is only that data?

My guess; server and consumer motherboards are very different. BMCs log a lot of data and on startup if the OS driver reads the log it can put whatever it wants in the crashdump. Consumer motherboards mostly only store the reason for last poweroff which the OS can read on next boot. Server MBs may also have a longer timeout before cutting power from a long-press.

Apparently from standby the power-off time on some laptops is much longer and you get a MANUALLY_INITIATED_POWER_BUTTON_HOLD which kicks off in the ~8 seconds from the article.

What about modern devices (such as laptops) that have a fixed battery? They shouldn’t rely totally on software to force a hard power off because that’s not safe. If the software hangs you cannot power down

Some laptops have a battery reset button for cases like this. For example lenovo has a pinhole where you can press a tiny button using a paperclip.

https://devblogs.microsoft.com/oldnewthing/20250107-00/?p=11...

The EC (embedded controller) controls the hard power off on a modern laptop, not the OS at all. That's why you can still power down in the event of a device lockup (thankfully).

It's all fun and games until the EC locks up.

Have had it happen on the Essential Phone and my MIL's Chromebook (don't remember the model). At least with the Chromebook, you can open it with a screwdriver and pull the battery. Better than waiting however many days for the battery to fully die so the EC resets.

until it stops making noise :|

My own PC doesn't take long at all to power off, although I know that for example on Lenovo laptops you need to hold that power button for quite long, I may count it next time I do it :)

suposedly the sepc for ATX was mentioing 4 seconds. But today's laptops take way longer.

The ACPI specification says: Additionally ACPI defines a fail-safe Off protocol called the “power button override,” which allows the user to initiate an Off sequence in the case where the system software is no longer able to recover the system (the system has hung). ACPI defines that this sequence be initiated by the user pressing the power button for over 4 seconds, at which point the hardware unconditionally sequences the system to the Off state. This logic is represented by the PWRBTN_OR signalcoming into the sleep logic.

the word "over" makes the difference I guess.

There seems to be some bits in Intel PCH chipset datasheets for that: Power Button Override Period (PBOP): This field determines, while the power button remains asserted, how long the PMC will wait before initiating a global reset. Encoding:

000b - 4 seconds

001b - 6 seconds

010b - 8 seconds

011b - 10 seconds

100b - 12 seconds

101b - 14 seconds

Others - Reserved

This bit is reset by DSW_PWROK de-assertion. (edited formatting)

Until the computer turns off...

It seems to be 7s, at least in ntoskrnl.exe 10.0.22621.1105:

  ; PopPowerButtonWorkCallback+0x1DF
  shr  ebx, 1          ; unpack elapsed milliseconds
  cmp  ebx, 0x1b58     ; 7000 milliseconds
   jb   ...            ; below threshold: skip crash path

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