Hardware Issues, suspected Motherboard or PSU

[nerang-coast]

Edit: The issue was the DisplayPort cable. Removing the cable eliminated the issue entirely and I could replicate the issue by using the DisplayPort cable again.

So I'm having this issue, and I'm not sure where the problem actually lies.
It started when I upgraded my computer system two months ago, where I replaced pretty much everything except the PSU. The computer ran fine for maybe a bit over a month, but then I began to have the odd issue where when turning on my computer it would sound alive, but nothing was being transmitted to any of my screens nor my keyboard or mouse. Only after several tries of turning the computer off and on again would it start up as normal.
Upon closer inspection, when turning on the computer, the motherboard would turn on seemingly as normal, but only one out of three fans on the GPU turned on and not the GPU itself, as well as the fan to the CPU cooling unit, but not the cooling unit itself or anything else. I googled it and it seemed to be a known issue with my new motherboard, so I tried a number of things; I changed around the positions of my memory sticks, changed it from dual channel to single channel, to just using a single memory stick. I reset the motherboard to factory settings. I updated the BIOS for the motherboard. I took everything apart and looked for any visible damages to the motherboard. But none of what I did helped.
So I put everything back together and sat it up and started it off and on again until it would normally start up. How ever, after having taken apart everything and put it back together, I started having another issue. My computer now unexplicably turns off, or partially turns off. On one occasion, everything but the motherboard seemed to shut off. No fans, no lights and no whirring from anything but the motherboard itself. On another occasion, my screens, keyboard and mouse turned unresponsive, and meanwhile, my GPU fans went full force, going as fast as they possibly could. There were no lights on the motherboard, but I was getting audio from a youtube video I was watching through my headphones. I manually turned the computer completely off after this.

I have no idea whats the true issue here. I'm starting to wonder if there is maybe something wrong with my PSU and there's an incorrect flow of power that is causing my computer to partially start up and partially shut down? My PSU is only four years old... Or is the issue just with my Motherboard, or could it even be the CPU?
As a side note of that... After upgrading my computer, my CPU usage has consistently been at 100%. There's no set program swallowing all the CPU, instead it seems to always be allocating 100% of the CPU to active apps, prioritizing the ones I am currently using. This can't be healthy for the CPU, and maybe this could be a cause for these inexplicable partial shutdowns?

My build is as follows:
Intel Core i7-7700K Kaby Lake Processor
MSI B250 Krait Gaming
HyperX Fury DDR4 2133MHz 8GBx2
EVGA GeForce GTX 1080 Ti
Corsair RM850 PSU
As well as a couple of SSDs/HDDs.

 

[1LiquidPC]

I would test with bare minimum hardware plugged in. A PSU or board could cause the issue, but a faulty/crimped PSU cable could cause a failsafe shutdown of sorts. I would test only with OS drive installed. Any logs in Event Viewer? Does on board video from motherboard work?

 

[nerang-coast]

I went and took my computer apart again and started it up with the bare minimum to begin with, running stable, and then continued to add piece by piece and it ran stable throughout and turned on as normal. After having put it back together completely, it now starts up with no problem, although I am still getting inexplicable crashes.
Prior to doing this, I have a number of Evend-ID: 29; Windows failed fast start up with error status 0xC00000D4, which is no longer occuring after having taken my computer apart and put it back together again.
What I'm still getting is Event-ID: 41; The system has rebooted without cleanly shutting down first, which I am sure is related to having to manually shut off the computer when it crashes. I'm also getting Event-ID 6008; The previous system shutdown at X on X was unexpected, the times of which correspond with when I normally shut down my computer last night and the night before.
Other than this, I am only seeing a bunch of Event-ID: 10010 and 10016, of which I am not sure could be related to the issues I'm experiencing.
Oh, and in the cases where my computer would not correctly start up, I have tried with the onboard video and it did not work.

I'm not sure what could have resolved the partial start up issue I was having, but the inexplicable crashes began after I went digging in my system. If it then is a cable that could be at fault, how am I to tell if it is faulty or not?

 

[1LiquidPC]

OK. When you mention current crashes requiring a manual shutdown, when do they happen? Any log file for them? What actually occurs during crash?

 

[nerang-coast]

There are no log files for it, no.
The first time it happened, I was just doing some web browsing when the monitors went black, the keyboard and mouse were unresponsive and nothing but the motherboard in the computer was giving off sounds and lights.
The second time it happened, I was running a virus scan with McAfee and browsing youtube meanwhile. Again, the monitors went black and the keyboard and mouse were unresponsive, though I still got audio and the fans on the GPU specifically went on max.
The third time it happened, earlier today, I was starting up an application while browsing youtube. Again, the monitors went black although the keyboard and mouse were still responsive and I was still receiving audio, although it cut out after roughly ten seconds.
In all these cases, I had to manually shut down the computer to restart it again. I can't find any correlating reasons to cause these crashes. The first two times the computer had been on and running for hours before this happened, while the third time it happened after just under an hour of having been turned on. Only the second time was I running something that could be considered strenuous for the system with a complete virus scan, but the first and second time I was doing practically nothing.

Considering it could be an external issue with the power cable or the wall outlets, I have changed the power cable and placed it in different and isolated wall outlets. The last time I did this was this morning after the third crash, and I'm still waiting to see if it will happen again.

 

[nerang-coast]

Had the fourth crash now after having tried it with a new power cable and on a different power outlet, so I think I can safely rule out external power management.

 

[1LiquidPC]

Have you tried other GPU drivers? When you replaced everything, was it a fresh OS install? Do you have another GPU to test by chance? Can you try other outputs or inputs on the monitors and GPU itself?

 

[nerang-coast]

I did not make a fresh OS install, no. But I tried putting in my old GPU and it made no difference and the computer still crashed.
When I went to put my current GPU back in, I also took out all of the power cables and put them back in one by one, making sure they all sat correctly. After doing this, I am now getting the issue where the computer won't start up correctly again.
I guess I'll try to make a fresh OS install.

Oh, and I have tried alternating between Displayport and HDMI on my monitors and the GPU, to no effect.

 

[1LiquidPC]

Very strange. Seems to point to a board issue at this point is my guess, as PSU has been fine for years. Not POSTing isn't going to be an OS issue itself.

 

[nerang-coast]

I put in my old motherboard and the issue persisted, arguably worse or at least differently so: I turned on the computer fine the first attempt, but after cleanly shutting it down and trying to turn it back on, the whole system was unresponsive. I turned the PSU off and on again, and the computer began to start up again... but unceremoniously shut off, and tried to restart itself again and again until I shut down the PSU.

I seem to have overlooked something, as I retracted my steps and I've finally managed to isolate what seems to be the cause. Using a DisplayPort cable. I use a DisplayPort cable for my main monitor and an HDMI for my secondary monitor, and I may have only swapped these two around but still used the DisplayPort cable each time. I recreated the issue again and again by using the DisplayPort cable, while everything runs completely fine with just HDMI cables.

So if this is truly the issue, why did it take so long to manifest like it did? I began to have this issue 2-3 months ago, but I bought my main monitor together with its DisplayPort cable 5 months ago.

 

[1LiquidPC]

Hard to say about the cable. Any power outages during that time? Possible excess current went through somehow, though this seems highly unlikely. To confirm, the issue is non-existent using HDMI only? Bad Displayport port?

 

[nerang-coast]

Yep. 10 out of 10 times using HDMI only, the computer cleanly shut down and started back up without any issue. Meanwhile, 9 out of 10 times with the DisplayPort cable, the computer would fail to start up. I did also try the other DisplayPort inputs on the GPU and on my second monitor and the issue persisted. I have gone over a full day with HDMI cables only and have not experienced any issues, nor have there been any errors in the event viewer.

 

[1LiquidPC]

Seems that it's the Displayport ports on your GPU since both monitors have the issue. Maybe a single controller on the card controls all DP ports. Does old GPU have Displayport?