Johnny Asia wrote:

I built this computer last summer, it has worked great until now. A
few days ago I lost internet connection, a clean reinstall of XP pro
didn't slove the problem, so I put in a USB wireless adapter, it works
fine. I bought a PCI express ethernet adapter and installed it
this morning. It worked fine for a few hours, then it suddenly stopped
working. It doesn't show up in device manager anymore, either.


Any ideas what the problem might be?


Thanks

Ethernet chips that support Wake On LAN, would have a power source provided
to keep them powered when the computer is sleeping. If that source, regulated
by the motherboard, was operating at the wrong voltage, it could damage the
device. You'd have to check the various standards, to find out what pin is involved.

This is a picture of the slot pinout. Tomshardware has reduced the resolution of
this photo, making it useless. I have a copy here, and pin B10 is labeled
"3VSB" and that would be an example of a sleeping card's power source.
In the diagram here, it is connected to V_3P3_Stby implying the proper
voltage on pin B11 would be 3.3 volts. But the source for that pin is
not the 3.3V rail of your power supply. They would start with +5VSB rail,
and a regulator chip on the motherboard, would make the 3.3V on that pin. A
problem with the regulator chip of the motherboard would cause a problem.

http://img.tomshardware.com/us/2004/.../pcie-slot.gif

Both PCI slots and any PCI chips with waking type functions, may have
that power source connected as well.

On this PCI slot pinout, the pin involved would be A14, labeled 3.3Vaux .

http://www.interfacebus.com/Design_PCI_Pins.html

And this Texas Instruments document, has a schematic with both PCI Express
and PCI slots. And you can see Vaux connected to both kinds of slots.

http://focus.ti.com/lit/ug/scpu023/scpu023.pdf

You could either live with the defect (being careful with add-in cards
from now on - Ethernet chips at least, will want to connect to Vaux). Or
replace the motherboard (under warranty or otherwise).

If you're handy with a multimeter, you could also probe your PCI Express
Ethernet card, and see what kind of voltage is present on B10. You might
not want to probe the slot itself, as the probe could easily slide off.

Paul