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Question PC shuts off randomly, fried Motherboard or unstable CPU?

May 27, 2020
TLDR & HW info at the end.

My CPU was running at 4,8 all core for maybe a year, decided to delid since it was running pretty hot and push it to 5ghz after that. Updated bios a couple of weeks before and it was still running fine for weeks after. Delid went fine, used der8auer tool and recommended metal liquid & silicone glue after watching the guide.

It was pretty late and while waiting for the glue I've decided to reconnect an older 1tb harddrive with some sketchy power cable(which was from an older PSU) and to throw in some RGB I had lying around while I'm at it, connected the 5V RGB connector to 12V pin on the MB. When I turned the system on the next morning the harddrive fried and the RGB header with it, great, not my finest or luckiest day, I just didn't noticed my MB had both 5v and 12v and apparently not all PSU cables are interchangeable. Feeling like a dumbass but still hoping nothing got damaged except the pins, cables and HD I've disconnected everything, changed cables, thrown out HD and tested until everything was running smoothly and fully connected again.

Continued to OC to 5ghz and more, tested temps, stability and benched for the rest of the day. Temps were exceptional(for my lil custom loop on a 240 radiator), performance was great and stable at all core 5ghz (Bluescreened @5.1).
Next day I start some game and the PC shuts off while playing for a while. Booted up again and watched temps while playing now, all good, water temp below 40°c, CPU core max temps all below 85°c. PC shuts off again...

Loaded default bios, standard clocks. Same deal, no luck after days while trying all kind of software/bios settings. PC starts shutting off while doing nothing in Windows, watching temps and volts in HWMonitor or just setting up in bios. Removed the whole setup, rebuild it from the ground up, exchanging RAM, PSU and running it without anything connected. Same problem, just sitting in bios for a couple of minutes to half an hour and the PC shuts off at random interval. CPU temp in bios 30°c, MB @ 35°c just before shutdown. Totally pissed off at that point I've decided to build a whole new system with basically just my GPU as "old hardware" in a new case, loop and it's been running fine for months.

My brother wants to get back into PC gaming so I'm building this nightmare back up again to save him some money.

The old RAM and 750w PSU (which both tested okay in my new system), the maybe broken motherboard and CPU with an even older AIO CPU cooler for easier access. Well nothing changed in the month it was sitting around as the problem still remains. There is no visible damage to the CPU or Motherboard (except that one 12V fried pin).

Before replacing the not so cheap motherboard and the even more expensive CPU I might as well ask you guys for any advice or experience. Did the CPU break in the OC or delid process or was one of the short circuits the reason the MB isn't working properly?

While waiting for a replacement MB I'm just sitting here hoping it's not the expensive CPU, for my brothers sake ofc.


  • i7-8700k delid (@default clock now) attempted OC with couple of bluescreens @5.1ghz (returned to "stable for a day" 5.0ghz after)
  • Strix Z370-F Gaming Bios Ver. 2401 with fried RGB 12V header
  • Corsair RM750i
  • clear cmos
  • nothing except AIO pump + fan connected (they're working)
  • temps ok, RAM ok
  • system shuts down randomly, in BIOS, Windows & Games
  • Motherboard or CPU broken?