What is the windows shut down sequence(regarding hardware)?

[perezalvarezhi]

I want to know what is the sequence that a windows 7(x64) machine(its an Asus motherboard just in case it is dependant of Motherboard manufacturer) follows when shutting down with respect to hardware.

Im making a project that uses an USB AC relay controller to switch a contactor (a switch with a coil) which gives power to the computer, basically it lets me turn on the computer using a button outside of a big industrial cabinet.

I just want to make sure that the USB is the last thing to loose power since the moment the USB looses power the contactor will not let energy flow to the PC and the hard drive might be damaged if it is not yet turned off.

Thank you for you answer!

 

[D.A.(Tony)Stewart]

your assumptions are wrong.

THe hardware and specifically the HDD is immune to the sequence of device shutdown.

However some software sequences may be incomplete if abruptly shut down too quickly so if you like to have clean logs during shutdown, add a time delay but there is no hardware risk.

Another method is to use the power switch with smart configuration of the Power switch to perform a sleep or hibernate or normal shutdown and startup, from the "soft" Power switch.

 

[perezalvarezhi]

THe hardware and specifically the HDD is immune to the sequence of device shut down.

Hi thank you for your answer, maybe the first question I should have asked is if there is any damage to my hard drive at all if the power is suspended to it before the computer turns off and after windows signals the drivers to turn off its devices. My experience when turning a computer off not gracefully is that windows checks if there was any damage to the HDD, therefore my fear.

I had the idea that after windows finished closing all the software and services running, it signals the drivers to shut down and as soon as they get that signal they perform whatever safeguards they have to do before turning off but that its windows independent and is all done by its controllers.

Do you think that if for some reason the Hard drive controller receives a shut down command, and the USB controller receives a shut down command at whatever order but the USB happens to turn off before the HDD, therefore cutting power to the computer's power source, will there be any damage to the drive?

 

[BradtheRad]

It's important for you to confirm that there is no chance of hard disk activity after USB shuts off.

Offhand I do not know, but there might be an article in the knowledge base at Microsoft.com, which states the exact power-down sequence.

If there is any doubt, then it is wise to delay for a few seconds before you cut power. A 555 timer IC is sufficient for this purpose.

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Cutting power during disk activity can result in loss of data, or loss of formatting.

It is (or used to be) possible for the heads to collide with (head crash) the disk if power is cut off before they are parked. This can result in lost sectors.