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Discussion Starter · #1 ·
I have a computer with an Asus Maximus XII Hero and sometimes (rarely) the machine will turn on completely by itself. Whenever I stop using the PC I completely power it down so it's never in sleep mode or hibernation. I'm on bios 2103 from this year and I've taken a look around at the settings but don't really see anything like power on by LAN or anything that looks like a likely culprit. Any ideas?

I've taken a look in windows as well and turned off fast-boot within my power settings so maybe that will make a difference as well.
 

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Replace the power cord.
 

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Probably a short on the motherboard or its components. I had once used a clip on heatsink on my NVMe drive, and it kept turning my computer on even after I had shut it down. It would power off, fans spun down and then turn on again.

I replaced the heatsink with the screw together type, and the issue went away. I suspect the clip had applied too much pressure or had touched a component on the NVMe drive.
 

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There's always the bios>advanced>APM Configuration>Restore AC Power Loss setting where you can choose to have it turn on after power loss. Or could be a short in your power cable.
Edit: Sleepycat's response seems more plausible. Maybe a stuffed cable that is sitting crooked in it's corresponding socket?
 

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Most likely a short, maybe the power button in the case.

If not that then a ghost who enjoys a game while you sleep. They get bored too.
 

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Since nobody has suggested it I assume it's a short on the motherboard or its components
 

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There's actually a lot of possible options. Some innocent, some indicating a fault.

I've had a look through the PDF manual for your board available on Asus' website, and to say that it's extracting the urine is putting it mildly. It gives no guide to the BIOS options, basically telling power users (who are the target audience) that they should only change BIOS settings with the "help of trained service personnel".

Anyway, while it sounds like you've had a brief look, check for anything that looks like Power-on-LAN, Power-on-USB, Wake-on-LAN, Wake-on-USB etc. On one of my systems even when fully shut down the mouse never truly goes to sleep, and the system would randomly boot up overnight because the mouse had moved enough on the trackpad to register. That was insanely frustrating until I figured it out.

Otherwise the PSU may be bad. I replaced every component of a build once except the PSU because I trusted the PSU tester... which basically lied, because the PSU was anything but OK. Replaced the PSU, no more random power ons or power offs. Sent it back to Corsair, got a replacement a few weeks later because the bad PSU was well out of whack.

I'm less sure about a short because most of the times I've seen systems shorted it's resulted in the magic smoke which makes it work coming out.
 

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Discussion Starter · #9 · (Edited)
Hmm, “restore ac power loss” in bios is turned off, my psu voltages in bios look perfect, and I checked all the cables to make sure they’re securely attached to the motherboard. I could try replacing the cord for the psu but it seems strange that it would cause it. I did make sure it was snugly attached though. In case I didn’t mention, my psu is a Corsair HX1000i that I got last year and has been very reliable. My caselabs Merlin sm8 case is kinda old though (I bought it in 2013)… maybe the power button could slowly be going bad? It happens rarely though so not a huge deal overall.
 

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you can try to remove the power button and just tune in on with screwdriver .
 

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You turn it on by completing a circuit on the two power on pins on the mobo, I'd start by unplugging the front panel/power switch and just turn it by shorting the two pins directly (requires care :)) - If that fixes it you'll know it's that switch/wire/power button that's the problem.
 

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In case I didn’t mention, my psu is a Corsair HX1000i that I got last year and has been very reliable.
Yup, the PSU that went bad for me was an HX850, which had been fine the week before. Not singling out Corsair here, just saying that stuff that was working fine can go bad without warning.
 

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Hmm, “restore ac power loss” in bios is turned off, my psu voltages in bios look perfect, and I checked all the cables to make sure they’re securely attached to the motherboard. I could try replacing the cord for the psu but it seems strange that it would cause it. I did make sure it was snugly attached though. In case I didn’t mention, my psu is a Corsair HX1000i that I got last year and has been very reliable. My caselabs Merlin sm8 case is kinda old though (I bought it in 2013)… maybe the power button could slowly be going bad? It happens rarely though so not a huge deal overall.
I just replaced the power and reset switches on my SM8, not because it was powering on by itself, but because the power button was getting finicky and not making good contact. The momentary switches are cheap enough on Amazon and I also bought two wiring harnesses (not necessarily needed) from PPC's for a few dollars each. Just be careful and don't reverse the led leads on the switches, it might blow them, IDK. All in under $30.
 

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I could try replacing the cord for the psu but it seems strange that it would cause it.
The professional electricians they deal with strange issues all day long.
In planet earth, a power button this will prefer to stop working than create a sort circuit.
 

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Check the BIOS for "Wake on LAN".
 

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Only other thing I see BIOS related is starting on the RTC (real time clock) but I think it's unlikely unless you already set it up each time.
 
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