Cold Boot Issue - suggestions?

Hi All,

I have bit of a strange cold boot issue. After being left off for a number of hours my PC will not cold boot until it has warmed up (~5 min). This started 3 days ago after 2.5 years of rock steady performance. The power light is constant.

After POST (no errors, no beeps) the system runs perfectly. It will warmboot (restart) without issues. In some cases it will cold boot start when the powerbar is turned on (without clicking my power button) after being off. It really is not consistent.

I have verified that all plugs and connections are seated correctly, run memory checks. I do not have spare PSU to test. Power levels seems to be adequate and the voltages are well within stock tolerances.

Is this the sign of a failing PSU? a weak CMOS battery, Bad ram, a bad Mobo or a bad power switch.

C2D 6850
OCZ stream 850W
Asus P5n32_E
4Gig OCA PC6400
Asus 8800 GT
7 answers Last reply
More about cold boot issue suggestions
  1. try to replace the cmos battery. see if that works.
  2. If your system will not cold boot without a warmup, how do you warn it up?

    I would guess that you have a small glitch in the standby power supply portion of your PSU.

    The standby power supply, among other things, provides power to the circuits that monitor the case power switch. If something is intermittently "stuck" in there, you could have a problem powering up your system.

    If you have a dmm, you can monitor the green wire. You should have 5 volts on the line as long as the PSU is plugged in and physically turned on. God chance that during periods of "warm up", it's not there.
  3. Is it the BIOS settings, what the PC does after A/C power loss?
  4. Thanks for the additional input folks! =) Happy squeeks to you all

    The problem is getting wierder. Yesterday the system would not power up at all, but voila this morning with both the power bar and PSU power switch set to off for 6 hours it booted - using the case switch.

    Yesterday I tried everything, second CMOS battery (no dice) - but my CMOS reset on boot this AM - maybe it needed to clear longer.

    I did the PSU 24-pin short test (fan and shorted 1 green/black pin) the PSU powers up nicely w/o warmup and the load fans spin happily. When the MOBO (and any other component) was added - no nice - until this AM.

    I tried shorting the PWR switch connectors to bypass the case power switch. (it is working now.. /sigh)

    I do not have a DMM - is there any way other way to check if that standby curcuit is iffy. It does sound like the problem as the system otherwise is stable. I assume that the "fix" is a new PSU.

    It has been suggested that some errant dust flake could be the cause - th ecase is pretty dust free but i found a few tiny free floating just bunnies this AM (thank you fans).

  5. Update - after powering down to test if it would reboot. No luck. At this point it takes a magic 8-ball to figure out when it will post again. Strangely when it does POST it does so quickly, flawlessly and w/o errors and can stay running for hours.

    So is the next step getting a new PSU or is it more likely something else ?

  6. I'd say that if you can borrow a known good PSU, borrow one.
  7. The problem has been resolved. Thanks Everyone!

    It turned out that the PSU was faulty after all and a replacement unit did the trick.

    Lesson learned: despite what many manufacturers and even a few enthusiasts claim, a VSD short test does NOT mean that the PSU is fine.
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