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Re: Strange reboot problem

Subject: Re: Strange reboot problem
From: Palindrome
Date: Wed, 19 Nov 2008 14:03:06 GMT
Newsgroups: uk.comp.homebuilt

Rob wrote:
"Janner" <[email protected]xxxxxxxxx> wrote in message news:[email protected]
I am experiencing a strange reboot problem with my PC. After turning off it will frequently reboot itself. This can happen anything from 1 to 10 minutes after the system has been shut down. However, it is not a full system restart. In fact it doesn't even get to POST. It will stay in this 'pre-POST' state for anything from a couple of minutes to several hours. It will then shut itself down. However, it may repeat this cycle several times before the system stays shutdown.
Is this likely to point to a Motherboard or PSU problem?

The system includes:

Asus P5B-VM Motherboard
Intel CPU Core 2 Duo E6600
Antec Sonata II Ultra Quiet Midi Tower case inc 450W PSU
2GB Corsair Value Select DDR2 PC5400D (4x512MB)
2x Western Digital 250GB Caviar SE16 SATA II 300 7200rpm 16MB cache
Windows Vista Home Premium

Any suggestions on the cause of this problem?
If this has recently started occurring on a previously working system,
I'd strongly suspect the PSU has developed a fault.  However, some
other device which uses the 5VSB supply could also have developed
a fault, so I'd unplug everything you can (eg USB devices etc) and see
if it goes away.
Some PSUs will keep their internal fans going after shutdown until
the innards are cool, but you should see no effect at all on the PC,
if it's that.

The SMPSU main supply is either running, or not. If it starts running without a trigger signal from the mobo, then it has a fault - but it cannot make the mobo behave in any other way than it would have, should the power supply have started up in response to a genuine trigger input. If the computer is showing things on the screen, eg the BIOS initial text, but not booting further - then, ISTM, not to be a power supply problem but something wrong with the system to which it is connected.
I'd check for WOL, wake on ring etc settings within the BIOS. It could
be that one of those is generating a false trigger - especially if
enabled but the system isn't configured to produce them (eg no modem
fitted, NIC is not connected to WOL socket, etc). The mobo is responding
to a false trigger, starting the main supply - but is then getting hung
in the BIOS routing, waiting for a "ready" signal from the modem/NIC
that isn't being correctly generated..

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