Re: CPU Core Voltage Too Low -> Crash? - Important Addition

Tech-Archive recommends: Repair Windows Errors & Optimize Windows Performance

From: Bob Dietz (rbdietz_1999_at_yahoo.com)
Date: 02/22/04 

Date: Sun, 22 Feb 2004 13:20:50 -0600

Don Cohen wrote:
> Hi Doug (and all),
>
> I did the swap of the memory modules, ran memtest86, still no errors.
>
> But then, I rebooted normally, and turned on "Motherboard Monitor". I set
> it to always 'stay on top' so I could see the CPU Core Voltage at all times.
> When I first turned it on, it registered 1.49V (according to Intel, the spec
> for my P4 chip is 1.50V).
>
> I then opened up a number of different applications (Photoshop, ThubsPlus,
> Internet Explorer windows, etc.) and watched the Voltage drop down to 1.46V,
> 1.48V, back up to 1.49V, etc. Back and forth - not quickly, just up and
> down. Never went higher than 1.49V.
>
> I opened up a program that shows digital camera pictures, and cycled through
> these very quickly. I watched the CPU voltage again drop to 1.46V, up a
> little, down again to 1.46V, and then bam!! - the crash occurred, same as
> all the other times.
>
> My thinking is that the CPU Core Voltage dropped lower than 1.46V and
> triggered the crash. As per Doug's comments, the Voltage Regulator for this
> is on the motherboard - hence the conclusion is that the motherboard is the
> source of my crashes.
>
> Please critique my thinking here, and confirm or refute what I'm inclined to
> conclude.
>
> Thanks.
>
> Don
>
>
> "Doug Knox MS-MVP" <dknox@mvps.org> wrote in message
> news:eM7mWQP%23DHA.2664@TK2MSFTNGP09.phx.gbl...
> Its possible, Don. Its also possible that the monitoring circuit is what's
> flaky, but that shouldn't cause a reboot, unless your BIOS would support
> turning off the computer to prevent damage, but then it should shut down.
> When you're dealing with voltages that low, there's not a lot of room for
> error.
>

Don, if a patient walked into your office and said, "My blood pressure is
130/85." Would you take him at his word or would you take your own reading?
If the patient brought in his own "blood pressure test kit", would you use
that to take the measurement or would you use your own equipment.

At this very moment, software readings on the following system:
    Motherboard: Asus A7V Rev3
    CPU: 1.3 Ghz (Morgan core)
    RAM: 512MB ( 2 x 256Mb SD-133)
    Harddisk: Western Digital 80Gb @ 7200RPM with 8Mb cache.
    Power supply: Antec Smart Power SL300S
are:
    +12.0V Rail: 12.46V
    + 5.0V Rail: 4.96V
    + 3.3V Rail: 3.57V
       CPU Core: 1.84V

At the same time, actual readings taken with a $60 Radio Shack 22-163 Digital
Multi-meter:
    +12.0V Rail: 12.22V
    + 5.0V Rail: 5.03V
    + 3.3V Rail: 3.37V
       CPU Core: (no way to measure)

This particular motherboard ALWAYS gives a low reading for the +12V and +5V
rails. It ALWAYS gives a high reading for the +3.3V rail. The core voltage
ALWAYS reads higher than what it has been set to in the BIOS. That has held
true in the case of three different power supplies.

The software readings off your motherboard may possibly be extreamly accurate.
But I wouldn't bet the team on it.

Personally, my next step would include all of the following.
    Unplug power and ribbon cables from every CD/DVD readers and/or writer.
    Unplug the printer.
    Remove any sound cards.
    If there's a modem and you're not using it (you've got broadband), pull it.
    Pull any other hardware you don't absolutely need.
    Remove one pair of RD-RAM sticks.
    Open Device Manager and disable any hardware you've temporarily removed.
    While you're in Device Manager disable any non-essential hardware on the
       motherboard. Eg. Built-in sound. Network adapter if you're using dialup.

If the system runs stable with minimal hardware, start adding things back one
item per day. If you get a random reboot, pull the last item and run the
system unchanged for a few days. If random reboots seem to disappear, assume
the item you removed is bad and continue adding items one per day. If the
random reboots crop-up again with these other items, start thinking
motherboard or power supply.

In that case, try to get the store you bought the power supply from to
exchange it for another. (Antec TruPower has a great reputation, but maybe
this one was produced on Monday morning after a wild weekend.)

Good luck,
Bob

Relevant Pages

  • Re: CPU Core Voltage Too Low -> Crash? - Important Addition
    ... > it to always 'stay on top' so I could see the CPU Core Voltage at all times. ... > is on the motherboard - hence the conclusion is that the motherboard is the ... This particular motherboard ALWAYS gives a low reading for the +12V and +5V ... Open Device Manager and disable any hardware you've temporarily removed. ...
    (microsoft.public.windowsxp.general)
  • Re: Power Supply Cause of Crashes? (Review)
    ... Next are the other hardware components. ... > voltage monitor). ... If motherboard control circuits have power: ... then purple wire (from power ...
    (comp.os.linux.hardware)
  • Re: varying voltage on 3.3v on Asus motherboard
    ... > i'm running asus pc prob for monitoring hardware temperature.. ... > recently, i've noticed that, voltage monitor gives signal of low ... > voltage on +3.3v for sometime & without doing anything come back to ... can help a technician to see, if the motherboard is ...
    (alt.comp.periphs.mainboard.asus)
  • Re: CPU Core Voltage Too Low -> Crash? - Important Addition
    ... You have noted that your voltage ... Is the Morgan core a Thunderbird? ... > This particular motherboard ALWAYS gives a low reading for the +12V and ... > Pull any other hardware you don't absolutely need. ...
    (microsoft.public.windowsxp.help_and_support)
  • Re: CPU Core Voltage Too Low -> Crash? - Important Addition
    ... You have noted that your voltage ... Is the Morgan core a Thunderbird? ... > This particular motherboard ALWAYS gives a low reading for the +12V and ... > Pull any other hardware you don't absolutely need. ...
    (microsoft.public.windowsxp.general)