Tuesday, December 11, 2012

BIOS Self-Down


How does BIOS of a computer shutdown it's power supply?

Explain technical process for system shutdown like with system booting process.

Is it possible for a computer to initiate it's complete power shutdown?
if so, how?

Additional Details

@Robert J,
"A low current logic supply is permanently on within the PSU"
Does that mean, computer is never power down completely, unless we pull the plug manually?

Let me suggest:
Can the system be completely self-shutdown, if a capacitor/condenser is used to temporary hold power to that 'low current logic supply' for an x amount of time?

I am interested in the process of 'entire system self-down' (true suicide) without external help.
Could that be possible (computers as well as for people)?

We also notice series of temporary self-downs (power cut) with electric bell (electromagnetism using magnetic field as an external/exclusive dimension to electric field).
Could permanent self-down be possible?

Very simply the BIOS is never completely powered down. That is what the BIOS battery is for.

[Robert J] 
Simply, there is a control pin in the main power supply connector that needs holding to 0V to activate the power supply.

That can be activated by a switch to turn on, and also a transistor to 'hold' power on.

If that transistor is turned off, the power supply shuts down.

A low current logic supply is permanently on within the PSU, to allow the on-off control circuit to operate.

[PC Power supplies generally also have a permanently-on low power 5V supply out which allows the power supply to be turned on again by motherboard logic (such as wake on keyboard / wake on LAN), but that is not an essential part of the normal on/off control.]

Edit - see the link below for the standard connector pinout.

Note pin 16, /PS_ON




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