P4S800 and HDD Activity LED

  • Thread starter Thread starter Bob Felton
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Bob Felton

I recently purchased a new computer using an ASUS P4S800 motherboard
(P4, 3GHz). I had been using it for about two weeks without any
problems while moving software and data from my previous computer
(PIII, 450MHz). The HDD activity LED only lit upon disk activity
during this time, even upon application of AC power to the power
supply (before actual turn-on). The last thing that needed to be done
to the new computer was to move the PCI modem card from the previous
computer to the new one. I powered up the machine and Windows XP Pro
found the new hardware (modem) and installed support. I then created
connectoids for connecting to dial-up accounts for backup (primary is
DSL) Internet access. I then decided to put the side plate back on
the computer so I told WinXP to shutdown. When the computer shutdown,
I noticed the HDD activity LED was still on! The power LED was off!.
This seemed odd to me, but I continued anyway. When I disconnected AC
power, the HDD LED went off. I then put the side plate on,
reconnected cables, and applied AC power. After applying AC power but
before pressing the ON switch, the HDD LED came back on! I then
powered up the machine. Everything worked properly. I left the
machine on while doing other things. Sometime later (1 to 2 hours), I
heard a very loud "pop" sound that came from the new computer and upon
investigation I found the machine was off and there was a definite
smell of burnt electronics coming from the power supply fan vent hole.
The computer would not turn back on. I took the machine back to the
computer store today and had the power supply replaced. The machine
now works again. However, the HDD LED still comes on as described
above when any (I tried two different ones in different slots) PCI
modem is installed. Now thinking there is a possible problem, I
removed the modem. The HDD LED is back to working like what I feel is
proper - only on during actual disk access.

My questions:
1. Does anyone know why installing a PCI modem causes the HDD LED to
work the way described above?
2. Did the described HDD LED action with modem installed have anthing
to do with the power supply going bad?

Thanks in advance.
 
Bob Felton said:
I recently purchased a new computer using an ASUS P4S800 motherboard
(P4, 3GHz). I had been using it for about two weeks without any
problems while moving software and data from my previous computer
(PIII, 450MHz). The HDD activity LED only lit upon disk activity
during this time, even upon application of AC power to the power
supply (before actual turn-on). The last thing that needed to be done
to the new computer was to move the PCI modem card from the previous
computer to the new one. I powered up the machine and Windows XP Pro
found the new hardware (modem) and installed support. I then created
connectoids for connecting to dial-up accounts for backup (primary is
DSL) Internet access. I then decided to put the side plate back on
the computer so I told WinXP to shutdown. When the computer shutdown,
I noticed the HDD activity LED was still on! The power LED was off!.
This seemed odd to me, but I continued anyway. When I disconnected AC
power, the HDD LED went off. I then put the side plate on,
reconnected cables, and applied AC power. After applying AC power but
before pressing the ON switch, the HDD LED came back on! I then
powered up the machine. Everything worked properly. I left the
machine on while doing other things. Sometime later (1 to 2 hours), I
heard a very loud "pop" sound that came from the new computer and upon
investigation I found the machine was off and there was a definite
smell of burnt electronics coming from the power supply fan vent hole.
The computer would not turn back on. I took the machine back to the
computer store today and had the power supply replaced. The machine
now works again. However, the HDD LED still comes on as described
above when any (I tried two different ones in different slots) PCI
modem is installed. Now thinking there is a possible problem, I
removed the modem. The HDD LED is back to working like what I feel is
proper - only on during actual disk access.

My questions:
1. Does anyone know why installing a PCI modem causes the HDD LED to
work the way described above?
2. Did the described HDD LED action with modem installed have anthing
to do with the power supply going bad?

Thanks in advance.
Click to expand...

I think somehow, the PCI modem has bridged +5V to +5VSB. Maybe the
PCI modem caused the demise of the power supply ?

Looking at the PCI spec, I can think of only two ways this can happen.
If the modem card is PCI 2.2 compliant, pin 14A connects to 3.3Vaux,
which I think is used to power the modem card so it can detect a
wakeup event (like Wake on Ring). Presumably, 3.3Vaux is derived from
+5VSB somehow on the motherboard. That is a long shot.

If the PCI card uses a spec rev number less than that,
(PCI 2.1), then pin 14A is unconnected. To get +5VSB, an older PCI
card would need one of those "Wake on LAN" three pin connectors
and signal cable, which carries +5VSB, PME, GND. Do you have
a cable like that connected to the modem card ? Perhaps the "sneak"
path is through such a cable. Maybe the modem card has joined +5V
to +5VSB through some fault or design feature on the card.

In any case, if this were me, I would leave that modem card sitting
in the junk bin for the time being. The funny behavior and popped
power supply might be more than a coincidence.

As always, this is Just A Guess,
Paul
 
Thanks for the reply, Paul. Most informative. I, too, think the
demise of the P/S was more than a coincidence. I believe the modem
insertion and P/S demise were related. I have left the modem out
until I determine if it was the cause. I will look up its
specification to which it "conforms". The modem does not have a cable
assy attached nor does it have a connector for one. The modem is
about 3 years old. Thanks, again, Paul.
 
My query to ASUS support explaining problem exactly as explained here
returned an absolutely useless response. All they suggested was to
ensure power supply in use was 350W or greater.

I have resolved the problem, however. I finally tracked down a manual
for the modem. Turns out there is one jumper on the card. It needs
to be removed when there is +5V standby power in the system. With
jumper removed, HDD activity LED now works normally with modem
installed.
 
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