Boot loop issue

KellerL · January 5, 2020

Hey ya all, seeking for help.

I bought a used pc, that in my opinion wasn't that old, considering used cpu/motherboard, maybe two three years? When the guy showed me the computer, he showed me
some stats of used ssd (m.2) that hit 92-94% of health. I believe that it came with the computer from the get go and wasn't changed during its lifespan.

specs:
i7 8700
msi z370 pc pro
gtx 1080
32 GB of 2133 (or whatever is close to this clock) ddr4, two brands, one Dell, other unknown, but all four of them made by Hynix
samsung 512 ssd m.2 (manufacture date sometime in 2014, no memorable name)
- psu (not a respected brand) ecopluspower eco+90 600W (this one https://www.ecopluspower.cz/inpage/atx-600wa-14-90/)

So to the problem. I used the pc for a month and one day it restarted while I was taking a leak. From then on, it boot looped. By that I mean, that cpu/gpu fans
started rotating and about second or less after it turned off, and on and off again, so on so forth. It never reached bios. I wasn't able to get a proper diagnose by a professional, so
did the basics myself. Motherboard has some debug leds, but they are all white and there is no description in manual. It consist of "boot, vga, dram, cpu", no hdd.
To be honest I am in the solve procedure for a whole two months now, so don't really remember what the debug lights showed back then, only know what it does now.

Basics I did:

- reseated everything - nada (by the way, ram stics were paired by their brands in channel slots)
- took out all ram stics and left only one in prefered slot, believe it was A2 slot - nope
- took out gpu and used igp instead - not a chance
- moved ssd (lets call it samsung) to m.2_1 slot (it was installed in m.2_2) - no change
- changed power cord - nope
- cleared cmos (first with a pins short, then with a battery removal) - nada
- used a laptop hardrive - no dice

A note: While troubleshooting I managed to run the computer for some time, like a day here, few hours there, before I started replacing things. It just bootlooped and then out of nowhere decided to run just fine.

So after all this and with a help on the local forum I decided it MIGHT be a faulty motherboard and so bought a new one, a cheap and basic one, but something to
get me going. It worked for a whole week and went dead again. Prior any actions I took out all but one stick of ram and pc booted just fine. So I started doing
stress tests, for 1, 2, and four sticks of ram, cpu and gpu and whole time the system worked just fine. I didn't push the stress tests to the limit though,
temperatures never got higher than 60°C. I also attempted to swap the motherboard for the old one to see, if it works. It didn't. So I googled around and found a
local "pro" who diagnosed the system for me, and concluded that the samsung (system) ssd might be the problem. I also gave him my old msi motherboard to test, if
it can be reused, since I believe it's better (in specs terms) that the new one. If it worked. He returned me the computer with system running on that old msi. So
I bought new m.2 ssd (let's call it WD). Yay. Surely, the computer didn't even bother coming up. Yay.

I talked to the guy, he was perplexed, as he claimed he used my cpu in his motherboard and it worked, he used all ram sticks elsewhere and it worked, he replaced
my samsung ssd with his m.2 ssd and the system worked and when he swapped ssds again for my samsung drive it eventualy died again. That die and upcoming boot loop
issue was erratic and random. So after this realisation that the computer doesn't work even with new wd ssd, he came up with an idea: he got himself into a time
frame when the computer worked and didn't show any issues with his ssd, and when he swapped for my samsung ssd he also fell out that "working" time frame, so he
concluded the ssd is the cuplrit.

So we decided to give my trusty old thinkpad hdd a second chance. I got it going, installed new system on it and it worked well for 5 straight days. With some
complete shut downs and many nights left in a sleep. Yesterday, again, computer rebooted on its own and a bootloop started, again. At first with whole system passing
bios, up to windows loading screen and keyboard/mouse activating, then reebooting, and later, after I shut down computer with psu switch, the system boot loops
withing 1-2 seconds. The debug leds light up cpu, then the light go out, a dram lights up and go out and then the computer dies.

Something tells me that the psu MIGHT be causing this dickery, but you know, it doesn't matter what my guts tell me. By now I would have a brand new pc if I was
cleverer. Well I have three options, if the problem is hardware bound, it is either ram going south, psu being shit or CPU malfunctioning. Since the pc bootlooped with igp as well and also worked with it in the meantime, gpu should be fine. And since it didn't boot up with new ssd, than maybe cpu have some pcie lines faulty and doesn't want to communicate with the ssd. Bu then, it started bootlooping with regular hdd as well.

Both motherboards are flashed to the newest bios.

By the way, my system received an update on thursday, but since the computer started bootlooping on saturday I don't think it's related.

Lukas

XAIXER · January 5, 2020

Try getting a new PSU from a better brand.

KellerL · January 8, 2020

Alright, will give it a try.

KellerL · March 7, 2020

Alright. Good call. Two months later with one or both ssd, one of which was called faulty, pc runs great. So far. it was a bitch to rout cables with Corsair PSU I got, wouldn't call it pretty, but hey, it's under desk and it works.

Thanks to XAIXER for finding the fault.