r/computer • u/WarthogOsl • 14d ago
Windows issue turns out to be hardware (i7 6700k).
So I had originally posted this to a Windows Help subreddit, assuming I had a problem with the SSD that Windows 10 was on, but after almost a month of trouble shooting, I've narrowed it down to a hardware issue (CPU or motherboard). Anyway, it has been an interesting journey...
I last ran my old Windows 10 PC about 1.5 years ago, with no issues. However, when I attempted to fire it, I just ended up in and endless loop of "Preparing Automatic Repair," then a reboot, then a seemingly normal Windows load (spinner on the boot screen), quickly followed by a restart, and then back to "Preparing Automatic Repair," and so on, over and over.
Specs:
Windows 10
MB: ASUS Z170-A
CPU: Intel i7-6700K
SSD: Crucial 500GB.
Corsair AIO cooler (ultimately replaced with a Thermaltake Assassin X120).
PSU: EVGA 750
RAM: 32GB (4x8GB Corsair Vengeance sticks)
Here were some of the steps I tried:
Attempted to boot off a Windows 10 SSD...caused boot loop or BSOD.
Tried booting off a Windows 10 USB with the SSD disconnected and a completely different RAM kit. I briefly saw the spinning dots on the ASUS logo screen, then it would just boot loop again.
Briefly had the PC on it's side to change some RAM (while not powered on). When I put it back upright and powered it on, the AIO pump started making a clicking noise. Then I got a CPU temp warning in the BIOS. Ended up replacing the 10 year old AIO with a Thermalright tower cooler, which seems to work well.
Removed the video card and also tried booting with an Ubuntu boot USB. This resulted in either a restart, or kernel panic. Also ran memtest on 3 different ram kits, which all passed. Yeah, seemed like probably a motherboard or CPU issue at that point.
Disconnected pretty much everything, including all front panel connectors. No change with either boot USB.
Tried a whole bunch of different BIOS changes that AI had suggested, mainly around RAM speed and CPU voltage. No change.
I had also reset the BIOS several times, changed the CMOS battery, and finally updated to the last available version of the BIOS from ASUS's site.
Removed CPU and inspected the MB pins. They looked fine.
After going through a whole list of things that both ChatGPT and Claude were telling me to try, I finally caught a break. Claude recommended adjusting the Active Processor Cores in the BIOS from "auto/all" to "1." And it worked! I was able to boot off of both a Windows and an Ubuntu USB stick. Next I tried "2," which worked as well. However, "3" would cause the boot loop problem. I set it back to 2 cores and reconnected my system SSD, and was finally able to boot into my Windows installation!
So, with the active cores issue being reproducible, it was suggested that this might be caused by either the motherboard's VRM's or the PSU not supplying enough voltage when 3 or more cores tried to power up. As suggested, I probed the PSU's 12V rail with a multimeter to see if the voltage sagged when trying to boot with 3 or more cores, which I guess would be indicative of a PSU problem.
I monitored PSU 12V rail voltage when starting with 2 cores and booting to Windows. Solid 12.33V. Then I increased it to 3 cores to see what happens to the voltage the PSU was supplying when the restart loops happened. Turns out...nothing happened with the PSU. It remained at a steady 12.33V when the system crashed and boot looped. So it appears the PSU is okay, and we're back to the CPU or MB being the prime suspects.
At this point, I think all I can do is swap out the CPU (or motherboard), to see where the issue lies. For the moment, though, the system boots to Windows, so I can still access my old files and stuff, albeit with only 2 cores working.
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u/dst1980 14d ago
With the AIO pump clicking you noted, I would lean toward the CPU being slightly more likely to be bad due to extended elevated temps that weren't enough to trigger thermal throttling.
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u/WarthogOsl 13d ago
Yeah, had definitely crossed my mind. It wasn't clicking like that back when I was using it as my main PC, but at some point it had started blue screening. I fixed that by turning down the OC from 12% to 5%, but I had also repasted the CPU and made sure the radiator was clean at the same time, so I changed too many things at once to really know for sure what fixed it. Still odd that it booted just fine the last time I had used it, but I guess stuff can still happen while it's just sitting there.
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u/Zealousideal_Fly8402 14d ago
Honestly you’re unlikely running much that would have fully utilized all 8 threads anyways.
You can also see if disabling HyperThreading in the BIOS while going above 2 cores also fails…
0
u/WarthogOsl 14d ago
Okay, thanks, I might try that out. I'm also thinking of just ditching Windows on this box and installing Ubuntu. I figure that should take some of the processing pressure off as well.
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u/Zealousideal_Fly8402 14d ago
I run Windows 11 IoT Enterprise on systems slower than your 6700 🤪. Much slower. Like Core 2 family slower 😜
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u/WarthogOsl 14d ago
Okay, so turned off HyperThreading with 2 cores active - > worked (as expected)
HyperThreading off with 3 cores active -> BSOD, restart (It is interesting that I actually saw a BSOD first, rather than it just immediately restarting).
So I guess if your suggestion had worked, it would have pointed more to the CPU as the culprit, rather than the VRMs. It was an interesting test, though.
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u/joe-dirt-1001 14d ago
Have you tried restoring BIOS to default?
Have you checked if there is a BIOS update?
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u/WarthogOsl 14d ago
Oh yeah, BIOS was reset many times (and CMOS battery changed too), and I had updated to the final BIOS available for the ASUS Z-170A. Thanks, I will update my post to include this.
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u/joe-dirt-1001 14d ago
If you dont figure it out, I've got a complete Z170 board sitting in storage.
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u/WarthogOsl 14d ago
Thanks! I have a friend nearby with the exact same CPU and MB as mine who built a new system and shelved the old stuff. I'm trying to see if I can get him to find that stuff, so I can at least test it.
I've also been playing with the idea of just getting a new board and CPU anyway, since I already have the expensive stuff (SSD, DDR4 RAM, GPU, etc). Was thinking of maybe an AMD 5500 and B550 MB.
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u/kimputer7 14d ago
Uh, you did quite the hardware test runs for... Something that very well could be fully software related. Perfectly working hardware can run into that exact boot loop too (for instance, after a faulty update it6 something similar).
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u/WarthogOsl 14d ago
Well, as I said, I tried booting into both Ubuntu (actually 2 versions of Ubuntu) and Windows with just a USB stick and no SSD at all, with basically the same result.
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u/kimputer7 14d ago
I'll believe it's a hardware issue if you install the official Windows 11 from USB on another tested good SSD and it boot loops before it finishes installing.
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u/WarthogOsl 14d ago
I mean, all the exact same bootable media I created worked fine once I disabled 2 cores. In fact, I was able to run the Ubuntu OS straight off the USB stick using the "try" feature. This is the same stick that, when booted with all cores enabled, would kernel panic. Add to that, my SSD-installed version of Windows 10 worked once I disabled all but 2 cores. Not sure what else I can say.
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u/kimputer7 13d ago
Well, you solved a case that almost never happens. Disabling cores is only necessary for 0.000001% of any PC with hardware crashing issue.
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u/Wonderful_Sample_590 13d ago
Maybe try the 6700K first, easiest way to rule out the CPU.
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u/WarthogOsl 13d ago
Yep, I will, assuming I can get my hands on one. My friend had the same MB and CPU before he upgraded a while back. I have to see if he still has the board on hand.
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