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Known Lecher
Jan 4, 2016


Problem description: "New" system build hangs prior to POST for no obvious reason and despite many attempts at troubleshooting.

Operating system: Windows 10 Pro 64-bit (not that it matters since I'm not getting that far)

System specs: Intel i7-4790k, Gigabyte Z97X-UD5H mobo, Cooler Master 212 EVO cooling fan, EVGA 850 G3 PSU, EVGA GTX 970 SSC, Kingston HyperX Savage 32GB Kit (4x8GB) 2400MHz DDR3 RAM

Recent changes/Attempted fixes: I'm taking the liberty of combining these two.

I'm going to give a fair amount of detail here because I'm hoping that, like some lovely computer-touching Sherlock Holmes mystery, the answer lies in an overlooked clue.

So the story begins a few months ago. My computer was running nice and stable, no blue screens etc etc., but it had a bit of a weird problem. I usually let it run 24/7 like a proper goon but whenever I had to shut completely down and restart, it would take a couple of tries before it would boot up - it would power up but just sit there with no video output and no POST. Once it was up, though, it would again run just fine for days/weeks without incident. It started taking more and more tries to restart (sometimes it would be on the first time, sometimes on the 10th), until a week or so ago it seemed like it just wasn't going to boot at all.

I figured my power supply had been slowly dying so I replaced my EVGA 750 G2 with an EVGA 850 G3 just in case. Plugged the connectors back in and lo and behold, still won't boot/POST just like before.

The next suspect seemed like the motherboard. I wanted to avoid the potential hassle of reinstalling Windows etc etc due to a hardware change, so I managed to find a guy selling the exact same motherboard here locally - secondhand, but he swore up and down it was working when he pulled it to upgrade. I have no reason to doubt him at this point.

It came in the mail, I moved over my CPU/cards/etc etc etc, and booted up. Lights and fans would spin up, it would power on for about 5 seconds, and then reboot in a loop. This motherboard has an LED readout of hexadecimal debug codes as it boots up/POSTs and it wasn't even getting that far.

I tried all of the following -

- Removed all graphics cards/memory/expansion cards/etc etc one by one until eventually I was booting with just the CPU and fan. Nope.
- Cleared the CMOS both by removing the battery and using the switch on the motherboard.
- Tried powering up with just the CPU/motherboard/fan outside the case on a nonconductive surface in case there was a short somewhere in the case. No luck.
- Removed the CPU cooler and thermal paste and reapplied thermal paste and re-seated the cooler. Haha no.
- A whole lot of swearing.

I moved the CPU/cooler back to the old motherboard and breadboarded it just confirm that yep, it still just booted and hung without POSTing on the old one, no reboot loop. As a long shot, I got a replacement CPU fan just in case the old one had a faulty connector and the system was shutting down because it didn't detect a CPU fan. No luck.

A FEW TIMES it would get partway through POSTing, hex codes would flash, but it never completed and it was completely random as to which times it would reboot after 5 seconds and no POST vs. 15-20 seconds and a partial POST.

For the hell of it I put it back in the case with memory and hooked up the various connections, but no GPU. It did the reboot loop as before, but after a few times it's now behaving like my old motherboard - powers up, but no POST and no reboot. It just sits there.

I basically have no idea what the hell could be causing this. The next possibility seems like the CPU itself, but it seems like even with a bad CPU the motherboard would attempt to POST, and if the CPU was starting to flake out I shouldn't have been able to run for days/weeks at a time between restarts without getting blue screens etc. I'm not going to be able to return a secondhand (or even a new) CPU here so I'm hesitant to sink several hundred more bucks into what seems like an unlikely gamble that that is the cause.

Help me computer goons, you're my only hope.

Location: What country are you in? China

I have Googled and read the FAQ: Yes

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Known Lecher
Jan 4, 2016


So after a little poking around, this motherboard has two switches to A.) Enable/disable dual BIOS and B.) boot from the main/backup BIOS. When I enable the dual BIOS, I get the "boot and hang" regardless of whether I select the main or backup BIOS. When I disable the dual BIOS I get the "endless reboot loop" (once or twice including a longer boot cycle with some partial debugging codes) regardless of whether I select the main or backup BIOS.

Pill Clinton
Jun 4, 2006

Feast for thought


You tried everything which I would have tried. No post issue usually are caused by CPU or motherboard failure or incorrect installation of CPU. You seemed to eliminate the motherboard one.

Can you borrow a compatible CPU from someone to test it out? Bring the system to a PC repair shop and ask for a compatible CPU to run a test?

Known Lecher
Jan 4, 2016


Good to hear I'm at least not overlooking something obvious. There aren't any repair shops in the immediate area, so I'm buying the cheapest compatible socket 1150 CPU that I could find to give that a try.

I would think if the CPU was going bad I would have been getting all kinds of blue screens and stuff, but maybe not? It seems like everything else has been ruled out, so who knows. I'll update when I've gotten the other CPU and tried it out.

Pill Clinton
Jun 4, 2006

Feast for thought


If a CPU was going bad, you would not get a BSOD (I think). Because BSOD requires the CPU to be working while the blue screen is going. An overheating CPU will get you BSOD, because at that point the CPU is still operational (the problem here is the heat).

If the new CPU is not going to help, then both of your motherboards might be bad. I am saying that you cannot, yet, rule out the chance that the secondhand mobo is also bad.

Zogo
Jul 29, 2003



Known Lecher posted:

- Removed all graphics cards/memory/expansion cards/etc etc one by one until eventually I was booting with just the CPU and fan. Nope.
- Tried powering up with just the CPU/motherboard/fan outside the case on a nonconductive surface in case there was a short somewhere in the case. No luck.

You need to use at least one stick of RAM to attempt a POST. Try different single sticks at a time.

Known Lecher posted:

I basically have no idea what the hell could be causing this. The next possibility seems like the CPU itself, but it seems like even with a bad CPU the motherboard would attempt to POST, and if the CPU was starting to flake out I shouldn't have been able to run for days/weeks at a time between restarts without getting blue screens etc. I'm not going to be able to return a secondhand (or even a new) CPU here so I'm hesitant to sink several hundred more bucks into what seems like an unlikely gamble that that is the cause.

It could be the CPU but multiple cases of RAM/PSU/motherboard failure are much, much more common.

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Known Lecher
Jan 4, 2016


Well I'll be damned, it apparently was the CPU. My cheapo G1820 Celeron test chip came, I plugged it and some RAM in, and it booted up as far as the hex debug code that correlates to 'checking for SCSI devices' then stopped. I'll probably go through the hassle of reconnecting and reinstalling everything just to make absolutely sure there's not something else before I tear it back down and a put in decent replacement CPU, but this is much farther than it had ever booted since before The Troubles.

Zogo posted:

You need to use at least one stick of RAM to attempt a POST. Try different single sticks at a time.

Thanks for this suggestion, before the CPU came I tried your idea and messed around with systematically testing two different single sticks (one at a time) in each slot but nothing. (Obviously, in hindsight.) Out of curiosity I tried no RAM once more with the replacement CPU, and the LED hex debug display did light up and stopped at a "reserved" hex debug code. So I guess this motherboard won't POST with no RAM but it'll at least give you some feedback.

Thanks Pill Clinton and Zogo for the replies.

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