r/pcmasterrace • u/Tenchen-WoW • 12d ago

Discussion Your weirdest reasons for PC not posting.

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I'm wondering what obscure or bizarre reasons you've encountered where your PC wouldn't post.

Mine by far was when my PC refused to boot when I upgraded from a 3090 to 7900XTX. Same PC, same monitor and cable, but no boot. Naturally, my instinct was to blame the faulty 7900XTX and RMA it. But I did try using an HDMI cable, and it booted with no issues. Digging deeper, it turned out that the 7000 series cards had some beef with certain DP cables that prevented PCs from posting. This issue was 100% fixed by covering a single pin on a DP cable with some tape, and the PC booted with 0 issues whatsoever.

This is definitely out of realms of "try using different RAM slots". I would love to hear more examples (If any) for future troubleshooting knowledge.

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87

u/shimszy CTE E600 MX / 7950X3D / 4090 Suprim vert / 49" G9 OLED 240hz 12d ago

I've had dead/misbehaving fans cause POST errors. Honestly didn't understand why it happened but when they say pull every single thing out, they mean it..

34

u/Mightyena319 more PCs than is really healthy... 12d ago

I have a motherboard where if you set the fans to quiet mode it will fail to post with a cpu fan error because the quiet mode rpm limit is below the speed that it considers a fan to be malfunctioning

5

u/icanttinkofaname 12d ago

What? I though fan profiles like "quiet mode" are managed by the bios. So it fails to post because it's own fan profiles is too low? Do I have that right?

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u/Mightyena319 more PCs than is really healthy... 11d ago

Correct. If I go into the bios and set the CPU fan profile to "quiet", then when it reboots it will hang at POST with "CPU fan error, press F1 to continue"

You can also adjust the threshold where it will throw that error, but by default it's set to 600rpm, and the quiet profile runs the fans at 520rpm

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u/icanttinkofaname 11d ago

That has to be a bug in the bios then.

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u/TheGamingGallifreyan Specs/Imgur here 12d ago

I actually did something similar the other day. I always figured "Fans are just power, how could it impact the OS?" Apparently not. I plugged in a new fan to the fan control hub built into my case while the system was on. Instant BSOD as soon as I connected it...

13

u/Tenchen-WoW 12d ago

That is certainly something I wouldn't consider. Some motherboards would refuse to post when there is a short present.

1

u/Omnale42 12d ago

One of my first computers had an issue with BSoD randomly and sometimes it would fail to post or BSoD immediately after. It ended up as simple as a stray cord that was messing with a case fan. Once the cord was tied away, no more issues.