Computer cut power during start up?

Zachary Roberts

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Dec 4, 2013
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Hi everyone, just over a month ago I built my own PC with 8gb corsair vengeance, 1tb sata3, corsair CX750 PSU, gtx 760 2gb GPU, WiFi, Intel Core i5 4570 CPU, and Gigabyte GA-B85M-D3H motherboard. Originally I installed Windows 7 Home Premium 64-bit on it and it ran perfectly fine. Yesterday I upgraded to Windows 8.1 Pro with Media Center and it ran fine during the install and it ran fine for the brief period I used it afterwards too. I then turned my PC off as it was getting late and I wanted to go to bed. I was satisfied that everything was working as I expected (because it was). This morning I received a new illuminated keyboard and gaming mouse in the post as, until now, I'd been using a bog standard USB keyboard/mouse. I fitted the new keyboard and mouse to the computer and then started the computer. It booted almost as far as the splash screen then the power cut out. No, we didn't have a power cut, but the power did cut out. It then proceeded to immediately restart after it shut itself off. Booted in fine this time. I checked Core Temp and the CPU temperature is perfectly normal. The Asus GPU tweak also show the GPU temperature as being perfectly normal. I checked device manager and no exclamation marks show next to any devices. I checked Event Log and, as you probably expect, there is a "Kernel Power" error number 41 critical log showing there. I honestly cannot expect the PSU is at fault. It's only a little over a month old and I've been using it for hours of intense gaming, without any issues at all. It's also got 750w so it can't be running out of watts, surely. As I said, this has only happened once and it did boot in perfectly fine after it shut itself down and started itself up again. But as far as I'm concerned it shouldn't even have done it that once. Any ideas?
 

SixCoreFiend

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Jan 11, 2014
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My first thought would be the power supply. Being a month old without a problem does not mean it is above reproach, and I actually bought a cx550 from corsair two years ago that had a very similar problem a few weeks into use. In my case, I kept on using it... until about a month after that I had a similar boot cut-out. The second time however resulted in an inability for the build to Post. My motherboard was found to be the culprit at that point, and though Intel happily replaced the motherboard, I'm fairly confident it was my PSU shooting out a spike that caused the issue.
 

Zachary Roberts

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I really hope it's not the PSU. That thing was a pain in the ass to install, and the motherboard even more so. Obviously it was my first time building a PC so it took me the best part of a few hours of hair raising moments of "how much pressure should I apply to get this damn thing to click into place?" Kind of moments. I don't really want to go through all that again. Obviously as I built it myself there's no manufacturer warranty or anything like that. This issue has only happened once and that once was with Windows 8.1. It never happened with Windows 7. I suppose since it's only happened once (so far) I can't really create a trend of events. Could it have been something to do with the new keyboard and mouse I plugged in? Maybe that's what caused it to reboot as it was installing drivers? It booted in fine the second time. Also, the PSU I bought has served me well so far. Why would it suddenly die? It's a corsair PSU and had tonnes of good reviews when I bought it (primarily WHY I bought it).
 
another plasable failure point could have been to many devices pulling to much power out of the usb ports (power surge)
asus anti surge kicked in and powered off the mb for safety. i would check online if anyone had power off issues like yours. some times if it is that issues some mb vendors will send out bios updates as they did with some apple products and intel chipset issues a few years ago.
 

Zachary Roberts

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These responses have got me worried rather than put my mind at rest. But, thinking about it from a diagnosis point of view, one occurrence isn't enough to go on. I have no choice really but to pretend it never happened...until if/when it happens again, in which case I'll let you guys know along with what I was doing at the time. This single occurrence I've had so far occurred during the initial startup process where Windows cut power and restarted automatically. Upon restart, it booted without problems. I've since shut down my PC again (the proper way...from within Windows). I'll resume normal usage until issues (if any) make me resume this discussion. But I have to clarify I was hoping this could have been a common software problem and I was hoping to blame Windows 8.1 for it. If this is indeed the start of a treacherous journey of hardware issues then I'm not going to be the happiest chappy.
 

Zachary Roberts

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Also, in case you didn't notice in my prior responses, let me clarify that my computer proceeded to "automatically" reboot after it "cut out". It didn't cut out and wait for me to press the power button before it rebooted. It actually immediately rebooted automatically. I've read somewhere that if a PSU cuts out it "cuts out" not reboots. Perhaps something else "may" be to blame?
 

SixCoreFiend

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And one of the ways it may protect against such an event is by prompting a reboot.

That said I (and this is just my personal opinion) feel that manufacturers put a lot of weight behind marketing "features" like that which do not offer the fool-proof-ed-ness that is suggested. There's no way for them to make their motherboard impervious to power events.
 
Check the power led to your graphics card. If the extra lead does not provide enough power to the card the card will attempt to take the power from
the PCI bus, when this happens on a card like this it will cause a voltage drop that will cause a reset signal to the CPU and the system will restart its initialization sequence in BIOS. The power supply can also correctly shut down the CPU if it detects two much draw on a feed line to the motherboard. In this case it will reset the POWER_OK signal to the motherboard and the motherboard will reset the CPU over and over until the POWER_OK signal is set from the power supply and you will be allowed to boot. (Cheap power supply will fake a power_ok signal)

end result in these case will be no error log and no bugcheck codes or minidumps
It is common for power supplies to fail in the first 30 hours. I think a lot of the failures are not detected until the units are power cycled and the power supply goes through its own checks at initialization.