Does your PC power on and off when a/c power is applied?

[Skyzoomer]

Bought a new Dell XPS-8900, i7, 12GB, Win10 from Costco. I have it plugged into a power strip along with my monitor and two external USB docking stations.

I shutdown the PC every night and when shutdown is complete, I turn the power strip off. When I switch the power strip on in the morning, the 8900 powers on for 2-3 seconds with it's power button bright white. Then it powers off, the power button white light goes off and it remains in this state. Then I press the 8900's power button and the 8900 does POST and then boots into Win10 normally.

I've worked on many PCs in the past (including other Dell XPS 8500 and 8700) and this is the first PC that does the momentary power on/off when a/c power is first applied.

I substituted two known working power supplies. With the 400 watt one, the symptoms are exactly like the original PSU that came in the 8900. The 500 watt one does the momentary power on/off and then the 8900's power button starts flashing amber in a 1-2 pattern. Pressing the 8900's power button does nothing and the 8900 will not power up. The power button just continues flashing. ----- These tests prove that the momentary power on/off when a/c power is applied is being caused by the motherboard and not by the PSU.

Googling, I see that some folks say that the momentary power on/off thing is normal for some PCs. My questions are why does it happen at all? Exactly what is the PC doing when it does the momentary power on/off thing when a/c power is first applied? --- Also, does your PC do it?

NOTE: This is not a discussion on whether to turn the power strip off or not. I only want to know what the motherboard is doing when it does the momentary power on/off thing when a/c power is applied.

 

[OlyAR15]

There is a BIOS setting that causes this. Alternately, don't turn off the power strip.

 

[VeryCharBroiled]

test of the psu initiated by the mobo when the psu initially gets power?

i have a dell mobo in my htpc with an antec 550 psu. it does this.

no other pc of mine does it, including the one i pulled the antec from. all other boards are non dell (gigabyte, asus).

 

[UsandThem]

There is a BIOS setting that causes this. Alternately, don't turn off the power strip.

+1

My PC does (did) this when I first connected it to power (only when the switch on the back of the PSU is left in the "on" position) , but I don't disconnect it daily like the OP does. If I leave the switch on the PSU set to "off" and unplug it, it does not do a quick power test when plugged back in.

I know the following question/confusion has been 'forbidden' in the OP, but I've never been good at following 'rules':

I understand some people like shutting down their PC because they don't like hibernate or sleep modes, but turning off the surge protector/power strip? What exactly is that supposed to accomplish? If there is a large surge enough surge come through the line, it's still going to destroy the PC.

 

[JackMDS]

Many of the Dells HP and others do it. That is the way they are designed.

When you turn a PC Off it is Not really totally Off, it stays in a dormant status. It is done for Networking, Remote Control, and WOL capacity.

In addition, the Computer's PSU has large capacitors that Spikes when they are empty and connected to the power. In the long run there can be damage from too frequent Spikes.

When you disconnecting often from the power (switching off the power strip) you really gain nothing and you reduce the life span of the computer.

 

[mnewsham]

When you disconnecting often from the power (switching off the power strip) you really gain nothing and you reduce the life span of the computer.

https://forums.anandtech.com/posts/38642723/
But how else can I confirm the intel AMT isn't sending out reports to the NSA when I sleep!? D: /s

 

[Skyzoomer]

*OlyAR15
I checked my XPS-8900’s BIOS and it wasn’t obvious which setting causes the momentary power on when a/c power is applied. Could you post the setting?
----------

*VeryCharBroiled
Thanks for posting your info. Your results confirm, like my tests did, that the Dell motherboard is causing the momentary power on/off. It does seem like a useless thing to do when everything is re-tested again anyway, when the power button on the PC is pressed to boot the PC up.
----------

*UsandThem
Interesting that your PC doesn’t do it if the switch on the PSU is set to off when you plug the power cord in, and still doesn’t do it when the PSU’s switch is switched on.

*jackMDS
Thanks for confirming that many Dells and HPs do it.


To all,
I feel that switching my power strip off saves having power applied to my monitor and two wall wart powered hard drive docking stations without having to switch each of them off individually. Note that the hard drives in the docking stations would be spinning all night or when I’m out of the house needlessly if the docking stations are not turned off. Also, if there is a power flux due to a car accident or tree branch falling on the power lines or whatever, the power flux won’t be applied to my equipment. Yes those things can happen when I’m using my PC but I can eliminate them when I’m not using my PC by switching off my power strip. Different strokes for ……

Thanks all for your input. I really appreciate it. I still wish someone who knows can explain exactly why some motherboards are designed to do it while the majority of other mobos don’t do it. Exactly what is the motherboard doing when it does it? Any Dell mobo designers lurking?

 

[VirtualLarry]

Those are probably AMT-capable business systems. Do they turn themselves on late at night in the AM too?

I had a couple of Intel S775 ITX boards, and they did that. Powered on briefly when plugged in, then shut off. Also, powered on late at night. Probably spying.

 

[OlyAR15]

It's been a while since I used the setting, but I recall it had to do with how the computer booted up after AC power loss. I also used to have a power bar that I used as a master on/off switch, before I bought my UPS.

The setting had 3 options: power off, resume last state, and power on. The first 2 options would cause your symptom: Since you turned off the PC before cutting power, when you turn on the power strip the PC would briefly turn on before the BIOS caused it to turn off. If you select power on, it will cause the PC to boot up as soon as power is restored, which is what you want to happen.

Edit:
Looking at my old Asus motherboard manual, the option is called Restore AC Power Loss.

 

[Billb2]

You need a power strip with individually switched outlets.

Something like this:

 

[Skyzoomer]

Those are probably AMT-capable business systems. Do they turn themselves on late at night in the AM too?

I had a couple of Intel S775 ITX boards, and they did that. Powered on briefly when plugged in, then shut off. Also, powered on late at night. Probably spying.

Not sure who you are responding to.
Skyzoomer

 

[Skyzoomer]

You need a power strip with individually switched outlets.

Something like this:

Actually I do have a power strip with individual switched outlets. But that would require switching off 3 outlets for my monitor and 2 external docking stations and then switching all 3 back on again. So I use a different power strip and just turn the master switch off to remove power to everything.

Thanks,
Skyzoomer

 

[mnewsham]

Actually I do have a power strip with individual switched outlets. But that would require switching off 3 outlets for my monitor and 2 external docking stations and then switching all 3 back on again. So I use a different power strip and just turn the master switch off to remove power to everything.

Thanks,
Skyzoomer

These are the things that keep me up at night

 

[piasabird]

I never turn off my power strip unless I want to work on the computer by opening the case. Computers and monitors are designed to go to sleep or go into hibernation and basically shut themselves off until you press a specific key. If you turn off the option for wake on LAN and wake on Mouse activity they will not come on unless you press some key on the keyboard. I have seen some problems when one of my computer's goes into hibernate and then when it wakes up the sound sometimes does not work. I think this has to do with the extra low power states of some of the newer CPU'S.

 

[Valantar]

Those are probably AMT-capable business systems. Do they turn themselves on late at night in the AM too?

I had a couple of Intel S775 ITX boards, and they did that. Powered on briefly when plugged in, then shut off. Also, powered on late at night. Probably spying.

My S775 Asus Rampage Formula does this. Flashes on for a second or two on power connect. Also does this on power on after connecting the power - a three-four second on-off-on cycle. It wakes from sleep on its own at all hours. I assume it's the NSA.

 

[Skyzoomer]

I never turn off my power strip unless I want to work on the computer by opening the case. Computers and monitors are designed to go to sleep or go into hibernation and basically shut themselves off until you press a specific key. If you turn off the option for wake on LAN and wake on Mouse activity they will not come on unless you press some key on the keyboard. I have seen some problems when one of my computer's goes into hibernate and then when it wakes up the sound sometimes does not work. I think this has to do with the extra low power states of some of the newer CPU'S.

The bolded above is similar to the reasons I shutdown my computers every night and get a fresh boot the next morning. I like to have a fresh copy of Windows in case stuff piled up during previous use. Not saying this is the correct way to do things but just how I do it.

Thanks for sharing your procedure,
Skyzoomer