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How does an ATX power switch really work

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  • CPUs
  • Switch
  • Computer
  • Power Switch
Last response: in CPUs
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November 4, 2001 2:46:25 PM

ok, so i'm basically wondering if there is anything wrong with the power switch on my Lian-Li pc 68 case. When i first built it, the system would not boot because it was not detecting the RAM, when it hung at this point pressing the switch for 3 seconds powered the computer down. Now, however, when the computer is booting, all i have to do is push the switch once and it shuts off. Is this normal? And in windows when i push the switch once it says windows is shutting down and turns off my computer, again, no 3 seconds. The only time i push it down for 3 seconds is when i put my computer in sleep mode, pushing it once is supposed to take it out of sleep mode, but I'm using RAID so my computer never comes out of sleep, but at that point pushing the button for 3 seconds shuts down my compter.

So how are these confusing shits actually supposed to work, I have not been able to find out.

More about : atx power switch work

November 4, 2001 5:22:00 PM

I'm not really understanding what you said, but you can check in your BIOS (under <b>Power Management Setup Menu</b>) and in Windows Control Panel (Power Management_Advanced tab). They define how your computer goes to <b>shutdown</b> or <b>standby</b>.

:smile: Good or Bad have no meaning at all, depends on what your point of view is.
November 4, 2001 5:43:01 PM

There's one little hitch to that. The settings in the BIOS typically don't actually take effect until after POST; even then, in some cases, the Shutdown/Standby feature of the power button may revert to hardwired-default behavior if the system locks up hard--and hardwired-default is usually to wait until the button is held for 4 seconds, then turn off.

Kelledin
<A HREF="http://www.linuxfromscratch.org/" target="_new">LFS</A>: "You don't eat or sleep or mow the lawn; you just hack your distro all day long."
November 4, 2001 6:41:51 PM

maybe this is a simpler way of asking it. In my bios there is something called soft-off and suspend. Right now it is set to soft off which means it will just shut the computer down i think. But when my computer did not start when i had bad ram in it, i would have to hold down the power button for it to shut off, but not during post, it just shuts off when i hit the power button instead of having to hold it for 3 seconds. Is this normal? What is it supposed to do set at soft off? and what is soft off exactly
November 5, 2001 5:42:00 PM

Soft off is shorthand for Software Off. In AT PSUs the On/Off is hardwired, i.e. You switch it on just like you switch on a light bulb (unless you're using a home control system, and god forbid you're using a microsoft os on that comp :wink: ).

ATX gives you the option of soft off. when you press the on/off button while the comp is on, the motherboard essentially tells the bios that this button was pressed, if an OS is ready, the bios will pass this message on to the OS. Now, your OS will decide what to do. In windows power management, if you set it to shut down, then it will shut down. If the OS is not ready yet, i.e. not yet loaded or does not support ACPI (is it ACPI or APM? ... can't remember), then BIOS will handle the message and do what you set it to do in the BIOS setup.

If the BIOS is not ready yet i.e. still doing the startup stuff, it will just do its default job (in some boards you have to press and hold it for 4 secs, in others its instant off).

You see, With an ATX PSU, you're computer is actually never off! Almost everything is done in software (in a sense). All you're perhipherals are getting some power. This is how you can have, network or modem signal powerup. A friend of mine put an infrared panel on his powerswitch button, you can switch it on with his Ipaq or one of them stupid handheld computers. I think its silly, cos you're only about a foot away when you're using the comp.

Save the environment, switch you're comp off from the mains when you're not gonna use it for a while, like before you go to sleep. If you're room is anything like mine, it will also help even further by switching off the millions of LED's. Sometimes I think I don't even need a light bulb... :lol: 


<font color=red><i>Poor is the pupil, who does not surpass his mentor</i> - Leonardo daVinci</font color=red>
November 5, 2001 6:02:35 PM

Yes, that's normal. "Suspend" is usually the hard-wired default. A lot of the settings in the BIOS (like the Suspend/SoftOff) won't actually take effect until the system has completed POST.

You probably noticed that the ATX switch connects to a two-pin header on the motherboard. When you press the ATX switch, it effectively shorts those two pins. When the system is in "SoftOff" state, it's waiting for those two pins to be shorted. It looks, sounds, and acts like it's unplugged, but the motherboard is getting some power--just the minimal amount of power to detect when the ATX switch is pressed. The only way to actually keep the motherboard from receiving any power is to disconnect power via unplugging the power cord or via a "hard switch" (the old AT-style power switch going straight to the power supply). That's "full power-off", a state in which the system is only powered by internal batteries (usually just the CMOS battery, delivering just enough power to track system time).

Kelledin
<A HREF="http://www.linuxfromscratch.org" target="_new">LFS</A>: "You don't eat or sleep or mow the lawn; you just hack your distro all day long."
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