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From: Mike Easter on 20 Nov 2009 13:51
I'm trying to conceive of the mechanism behind this hardware problem
even if I decide to not repair it, I would like to have a better
understanding of what is going on. I've brought this problem up here
before in a different form.

Here is the hardware: mobo ECS 741GX-M2 which is a AMD socket A using a
AMD Geode NX-1750 which board has integrated everything, video, sound, &
ethernet via the SiS chipsets 741GX north & 964L south. It has a 250W
PS. Currently only one of the two ram slot/s are/is populated with 1G
DDR ram.

Here is the hardware problem which occurs infrequently under very
limited software circumstances, but is the same with various operating
systems such as XP or Mint or Mandriva and various browsers such as
Chrome or Firefox. While reading a webpage which extends below beyond
the screen's window, I typically use the mouse on the vertical slider
rather than paging; that is, I slide the window slider so as to expose
that lower part of the page which goes beyond the window's edge.

Occasionally, about once a week or so, while performing that operation,
the machine abruptly shuts down. Instantly.

During this shutdown, the following conditions can be observed. The
front power light is off. The two yellow and green ethernet lights at
the rear remain lighted. Most significantly, the front powerswitch does
not work to power back up. The relationship between the mobo and the PS
is 'dead'.

In order to restore funcitonality, it is necessary to turn off the PS's
rear switch. During this type of shutdown, whatever gets reset doesn't
happen 'instantaneously'. It requires a few seconds, say 5-8. The
other thing which requires a few seconds is those little lights beside
the ethernet port. Once those seconds have elapsed and the ethernet
lights are off, I can turn the rear PS switch back on, then the front
panel power switch works again and the machine powers up and everything
is operational for a considerable time, maybe more than a week. Maybe
only a few days.

I routinely view webpages in the manner described, and almost 100% of
the time this viewing method works. But occasionally I get the shutdown
described. Presently I get the shutdown under no other software
conditions that I have found.

However, if I put 2 1G ram sticks into the slots, I have a bigtime
problem with this type of shutdown under all kinds of other conditions.

Since replacing the PS is a popular troubleshooting method for some
power related mysteries, I'm sure that replacing the PS would be
informative, because the result might be that a new PS causes everything
to work properly with 1 or 2 1G sticks of ram and the whole problem is
relatively undiagnosed but solved. The result of that PS replacement
might also be that under conditions of a new PS that the (mobo) failure
problem would occur just as before, in which circumstance the next
experiment would be to replace the mobo.

However, rather than replace anything for information, I would like to
have a better understanding of what the 'meaning' of the change in the
demands on the power that the movement of the window slider causes. I
would also like to have a better understanding of what is the meaning of
the power light on the front panel going off but the ethernet lights
staying on.

I would also like to have a better understanding of the what kind of a
relationship between the mobo and the PS can cause the two of them to
need to be reset because of some kind of power fault protection which
resetting requires to shut down the rear switch for some seconds. And
how come it takes some seconds for the ethernet lights to go off when
the rear switch is shut off.


--
Mike Easter

From: Paul on 20 Nov 2009 18:08
Mike Easter wrote:
> I'm trying to conceive of the mechanism behind this hardware problem
> even if I decide to not repair it, I would like to have a better
> understanding of what is going on. I've brought this problem up here
> before in a different form.
>
> Here is the hardware: mobo ECS 741GX-M2 which is a AMD socket A using a
> AMD Geode NX-1750 which board has integrated everything, video, sound, &
> ethernet via the SiS chipsets 741GX north & 964L south. It has a 250W
> PS. Currently only one of the two ram slot/s are/is populated with 1G
> DDR ram.
>
> Here is the hardware problem which occurs infrequently under very
> limited software circumstances, but is the same with various operating
> systems such as XP or Mint or Mandriva and various browsers such as
> Chrome or Firefox. While reading a webpage which extends below beyond
> the screen's window, I typically use the mouse on the vertical slider
> rather than paging; that is, I slide the window slider so as to expose
> that lower part of the page which goes beyond the window's edge.
>
> Occasionally, about once a week or so, while performing that operation,
> the machine abruptly shuts down. Instantly.
>
> During this shutdown, the following conditions can be observed. The
> front power light is off. The two yellow and green ethernet lights at
> the rear remain lighted. Most significantly, the front powerswitch does
> not work to power back up. The relationship between the mobo and the PS
> is 'dead'.
>
> In order to restore funcitonality, it is necessary to turn off the PS's
> rear switch. During this type of shutdown, whatever gets reset doesn't
> happen 'instantaneously'. It requires a few seconds, say 5-8. The
> other thing which requires a few seconds is those little lights beside
> the ethernet port. Once those seconds have elapsed and the ethernet
> lights are off, I can turn the rear PS switch back on, then the front
> panel power switch works again and the machine powers up and everything
> is operational for a considerable time, maybe more than a week. Maybe
> only a few days.
>
> I routinely view webpages in the manner described, and almost 100% of
> the time this viewing method works. But occasionally I get the shutdown
> described. Presently I get the shutdown under no other software
> conditions that I have found.
>
> However, if I put 2 1G ram sticks into the slots, I have a bigtime
> problem with this type of shutdown under all kinds of other conditions.
>
> Since replacing the PS is a popular troubleshooting method for some
> power related mysteries, I'm sure that replacing the PS would be
> informative, because the result might be that a new PS causes everything
> to work properly with 1 or 2 1G sticks of ram and the whole problem is
> relatively undiagnosed but solved. The result of that PS replacement
> might also be that under conditions of a new PS that the (mobo) failure
> problem would occur just as before, in which circumstance the next
> experiment would be to replace the mobo.
>
> However, rather than replace anything for information, I would like to
> have a better understanding of what the 'meaning' of the change in the
> demands on the power that the movement of the window slider causes. I
> would also like to have a better understanding of what is the meaning of
> the power light on the front panel going off but the ethernet lights
> staying on.
>
> I would also like to have a better understanding of the what kind of a
> relationship between the mobo and the PS can cause the two of them to
> need to be reset because of some kind of power fault protection which
> resetting requires to shut down the rear switch for some seconds. And
> how come it takes some seconds for the ethernet lights to go off when
> the rear switch is shut off.
>

The motherboard and power supply have protection features.

1) Processor THERMTRIP. Modern processors have an overtemperature detector,
which can be used by motherboard logic. Your S462 motherboard, would need
an 8 pin DIP connected to the processor thermal diode, to give the
equivalent overtemperature protection. (That is what my old Nforce2
motherboard uses.) Earlier S462 motherboards relied on BIOS mediated
control of overtemperature detection, which wasn't always reliable.
Newer designs are "all-in-hardware", to ensure they trigger properly.

2) Vcore regulator overcurrent detection. The regulator may "latch-off" if
it detects a problem. The Power Good signal from the circuit, is one
signal the regulator sends, to the rest of the motherboard logic, indicating
how happy it is.

3) PSU overvoltage/overcurrent protection (internal to the PSU). This
may cause latch-off, and require cycling the power, in order to
remove the supervisor latched off state info.

Circuits powered by +5VSB can be used to "remember" the fault, and
prevent instantly repeating it. Requiring the user to turn off the
power supply, to get the computer to work again, means a human
will be present when power is applied again.

As to how some of these features would be wired up, it is up to the
motherboard designer to decide what to do with them. The PS_ON# logic
for example, is already pretty extensive, including connections to
the Southbridge and Super I/O chip. Additional jelly-bean logic may
be used to incorporate safety features into the chain of logic, for
things that the major chips haven't taken into account.

If you want an interesting test to try, use Prime95 Torture Test from
mersenne.org/freesoft . In your particular case, you'd want to run
"small FFTs", so that the Torture Test runs within CPU cache, and
makes the CPU get as hot as possible. Can the processor and Vcore
run the Torture Test for at least ten minutes ? Does anything overheat ?
Are your symptoms reproduced ? Did the computer shut off ?

If the computer shut off, run the test again, and use Speedfan to
monitor temperatures as best you can. Do you see any temperatures
spiking as soon as Prime95 starts the Torture Test ?

Looking at a picture of your motherboard, it looks like Vcore may be
powered from +5V. Some regulators have UVLO (under voltage lock out),
and if the main power supply connector isn't making good connections
(low impedance), that can be enough to trigger protection on Vcore.
If the main power connector was loose, the pins can burn and contact
surfaces degrade. Pull the main connector and examine it for
damage.

If each motherboard documented how all this stuff worked, and what
symptoms to expect, it would then be possible to make a fault tree
for your consideration. But as it is, with no documentation, we
can only speculate what the side effect would be from some of these
things. They add safety features, but don't go out of their way
to tell you what they are, or how they're tied into PS_ON#.

Paul
From: Andy on 20 Nov 2009 19:37
Start by using a multimeter to measure the power supply voltages at
the ATX power connector.

On Fri, 20 Nov 2009 10:51:49 -0800, "Mike Easter" <MikeE(a)ster.invalid>
wrote:

>I'm trying to conceive of the mechanism behind this hardware problem
>even if I decide to not repair it, I would like to have a better
>understanding of what is going on. I've brought this problem up here
>before in a different form.
>
>Here is the hardware: mobo ECS 741GX-M2 which is a AMD socket A using a
>AMD Geode NX-1750 which board has integrated everything, video, sound, &
>ethernet via the SiS chipsets 741GX north & 964L south. It has a 250W
>PS. Currently only one of the two ram slot/s are/is populated with 1G
>DDR ram.
>
>Here is the hardware problem which occurs infrequently under very
>limited software circumstances, but is the same with various operating
>systems such as XP or Mint or Mandriva and various browsers such as
>Chrome or Firefox. While reading a webpage which extends below beyond
>the screen's window, I typically use the mouse on the vertical slider
>rather than paging; that is, I slide the window slider so as to expose
>that lower part of the page which goes beyond the window's edge.
>
>Occasionally, about once a week or so, while performing that operation,
>the machine abruptly shuts down. Instantly.
>
>During this shutdown, the following conditions can be observed. The
>front power light is off. The two yellow and green ethernet lights at
>the rear remain lighted. Most significantly, the front powerswitch does
>not work to power back up. The relationship between the mobo and the PS
>is 'dead'.
>
>In order to restore funcitonality, it is necessary to turn off the PS's
>rear switch. During this type of shutdown, whatever gets reset doesn't
>happen 'instantaneously'. It requires a few seconds, say 5-8. The
>other thing which requires a few seconds is those little lights beside
>the ethernet port. Once those seconds have elapsed and the ethernet
>lights are off, I can turn the rear PS switch back on, then the front
>panel power switch works again and the machine powers up and everything
>is operational for a considerable time, maybe more than a week. Maybe
>only a few days.
>
>I routinely view webpages in the manner described, and almost 100% of
>the time this viewing method works. But occasionally I get the shutdown
>described. Presently I get the shutdown under no other software
>conditions that I have found.
>
>However, if I put 2 1G ram sticks into the slots, I have a bigtime
>problem with this type of shutdown under all kinds of other conditions.
>
>Since replacing the PS is a popular troubleshooting method for some
>power related mysteries, I'm sure that replacing the PS would be
>informative, because the result might be that a new PS causes everything
>to work properly with 1 or 2 1G sticks of ram and the whole problem is
>relatively undiagnosed but solved. The result of that PS replacement
>might also be that under conditions of a new PS that the (mobo) failure
>problem would occur just as before, in which circumstance the next
>experiment would be to replace the mobo.
>
>However, rather than replace anything for information, I would like to
>have a better understanding of what the 'meaning' of the change in the
>demands on the power that the movement of the window slider causes. I
>would also like to have a better understanding of what is the meaning of
>the power light on the front panel going off but the ethernet lights
>staying on.
>
>I would also like to have a better understanding of the what kind of a
>relationship between the mobo and the PS can cause the two of them to
>need to be reset because of some kind of power fault protection which
>resetting requires to shut down the rear switch for some seconds. And
>how come it takes some seconds for the ethernet lights to go off when
>the rear switch is shut off.
From: larry moe 'n curly on 21 Nov 2009 10:25

Mike Easter wrote:

> mobo ECS 741GX-M2 ... socket A
> integrated everything, video, sound, & ethernet via the SiS chipsets
> 741GX north & 964L south. It has a 250W PS.

> While reading a webpage which extends below beyond
> the screen's window,

> Occasionally, about once a week or so, while performing that operation,
> the machine abruptly shuts down. Instantly.
>
> During this shutdown, the following conditions can be observed. The
> front power light is off. The two yellow and green ethernet lights at
> the rear remain lighted. Most significantly, the front powerswitch does
> not work to power back up. The relationship between the mobo and the PS
> is 'dead'.
>
> In order to restore functionality, it is necessary to turn off the PS's
> rear switch. During this type of shutdown, whatever gets reset doesn't
> happen 'instantaneously'. It requires a few seconds, say 5-8. The
> other thing which requires a few seconds is those little lights beside
> the ethernet port. Once those seconds have elapsed and the ethernet
> lights are off, I can turn the rear PS switch back on, then the front
> panel power switch works again and the machine powers up and everything
> is operational for a considerable time, maybe more than a week.

Brevity, Mike, brevity. :)

The fact that your computer suddenly turns off occasionally AND you
have to flip its rear power switch to restore operation indicates the
power supply is at fault and its overcurrent/overpower protection
circuitry has triggered. Turning off the PSU resets that circuitry.
And if your PSU is the original one for your Socket A motherboard,
it's probably at least 5 years old and has some worn-out electrolytic
capacitors inside it (www.BadCaps.net has tons of information about
this). Worn caps can really reduce the power capacity of a PSU.
From: Mike Easter on 21 Nov 2009 13:23
larry moe 'n curly wrote:
> Brevity, Mike, brevity. :)

I'll try. :-)

Paul wrote:
> If you want an interesting test to try, use Prime95 Torture Test from
> mersenne.org/freesoft . In your particular case, you'd want to run
> "small FFTs", so that the Torture Test runs within CPU cache, and
> makes the CPU get as hot as possible. Can the processor and Vcore
> run the Torture Test for at least ten minutes ? Does anything overheat
?
> Are your symptoms reproduced ? Did the computer shut off ?

No. No. and No.

I don't see how these explanations help me understand...

-1- why this symptom is only reproducible with one specific type of
scrolling in a browser window regardless of OS or browser
-2- why part of the mobo still has power to light the ethernet lights
after general failure protection shutdown


--
Mike Easter

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