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My friend got done with his first build yesterday. It all works flawlessly, however something concerns him. When he first powers up his computer, the motherboard light and fans start up, but then it powers down a second later, waits a second more, then proceeds to normal boot. Why is this? Could it be because something other than the hard-drive is the primary boot device? That's what I suspect.

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What has your friend built? The desktop tower? And what OS is supposed to be running on the HDD? –  AniDev Dec 17 '10 at 2:58
    
@AniDev OS is irrelevant to the OP's question. –  barlop Dec 17 '10 at 4:00
    
I very much doubt it's hard drive related. Is it the monitor that flicks on Iand off, i've seen that. Or it could be i've seen this on asus motherboard, the fan goes on full blast at the start, then because qfan is enabled(and rightly so), it goes quieter. that's not poewring down. If qfan was disabled it'd be full blast all the time. You can test that. And see if the powering up and down that you feel is really the cpu fan speed. ULtimately, the best you can do is fiddle in the BIOS and see if anything affects it. –  barlop Dec 17 '10 at 4:06
    
The operating system is Windows 7 64-bit. The motherboard is a Gigabyte board. All the lights (fan and motherboard) light up with the power on, then they go off, then they kick back on. It appears that the entire system shuts down, not just the lights or the fans aesthetically; the entire power seemingly goes out. This doesn't affect the performance, however. Once the system is up and running, it's fine. –  Reznor Dec 17 '10 at 5:15
    
This happens with my Intel S5000 motherboards, since all 160-odd servers show the same behaviour I've always assumed it was part of the POST –  Tog Dec 17 '10 at 21:44
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1 Answer 1

This is normal POST behaviour on some boards that, IIRC, do the following procedure:

  1. BIOS self-test (checksum comparison)
  2. Reboot
  3. CMOS self-test (checksum comparison)
  4. Do prolonged tests (regular POST)
  5. Bootstrap

This is especially common on boards with a redundant BIOS in place ready to be flashed if the main is corrupt (and thus fails its self-test).

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