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I seem to have quite a temperamental problem, occasionally when booting my machine all the fans start at 100% and there is no POST, no system beeps, nothing (have to power down holding power button for a few seconds).

Switching everything off at the mains for a period of a few minutes seems to resolve things (this isn't consistent but certainly works 90% of the time).

I'm guessing this must either be caused by the motherboard or power-supply (leaning toward motherboard). Am I correct in thinking this? What steps could you folks recommend to pin-point the problem?

  • Mobo - Gigabyte GA-EP35-DS3
  • PSU - Be Quiet! Dark Power Pro 650w
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Power buttons on modern systems are "soft-switches" which tell the motherboard to tell system (including the power supply) to wake. There are many conditions (temperature sensors, under-voltage, software told me to suspend, I don't feel like it, etc.) that the reset line isn't pulled by the motherboard. Pulling it from the wall allows on-board capacitors to drain thus causing the machine to forget that it (erroneously) doesn't want to start.

First ensure that your BIOS is the latest and see if that helps.

added based on comment:

Something is making the motherboard think that it shouldn't turn on, letting the caps drain by pulling the mains is clearing the problem but it isn't solving it. I'd check what system sensors I could with something like SpeedFan to rule out that your cooling is bad (and slowly frying your machine). It is also possible that the "do not boot" condition is falsely latched on, but check what you can before ignoring the symptom.

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Sorry should have mentioned in the question that I'd already updated the BIOS. Seems like the capacitors on the Mobo draining is allowing the system to boot. Thanks for the answer! Thanks for the answer! – davbo Jun 23 '10 at 22:57
sure, but see "added" above. – msw Jun 23 '10 at 23:08

I think your right about it being the motherboard. I don't think it is very likely that it is the power supply. You can try unplugging everything (dvd-drive, webcam...) except the essentials which will give the power supply more juice to work with. If the problem continues, it is probably the motherboard.


I have the same problem on my computer. When I unplug the power for about 10 seconds (or until the little LED light on the motherboard goes out) and then plug it back in again, it always starts right up.

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I've already tried removing all the non-essential cables from the (modular) PSU. This allowed it to boot but since the main power was off when removing the cables I was half expecting it to boot. Since it's so temperamental it's difficult to debug. Certainly thinking it's the motherboard more now though. Thanks for the answer! – davbo Jun 23 '10 at 23:02

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