P4C800-E DL Lan Disconnects

  • Thread starter Thread starter Barry
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Barry

The onboard LAN on my P4C800-E DL disconnects and reconnects every ten
seconds.
Have installed latest drivers, enabled in BIOS.
PCI card LAN works fine.
Anybody got any ideas other than disabling and using the PCI?
Barry
 
"Barry" said:
The onboard LAN on my P4C800-E DL disconnects and reconnects every ten
seconds.
Have installed latest drivers, enabled in BIOS.
PCI card LAN works fine.
Anybody got any ideas other than disabling and using the PCI?
Barry
Click to expand...

It could be the autonegotiation function is in a loop because
of some connectivity problem. Just a guess.

I've had one Asus motherboard with a dirty Ethernet connector.
Plugging and unplugging multiple times, seemed to clean the
residue off the contacts.

If you own a second computer with a Marvell Gigabit ethernet
interface on it, it may be equipped with Virtual Cable Tester
(VCT) software. VCT uses Time Domain Reflectometry (TDR - a
similar method to how radar ranging works). VCT can detect
opens or shorts. If you connect two Gigabit interfaces
together, all four pairs in the Ethernet cable are used -
VCT should indicate that all four pairs are connected and
properly terminated. That is the only easy way I know of,
to tell whether cable and connector are making good contact.

http://marvell.com/products/transceivers/singleport/VCT_White_Paper.pdf

Paul
 
Thanks for that, I have another PC, I'll have to read your notes carefully.
The Firewire doesn't work either although I gather it is a bit sniffy on
these boards anyway. Since the LAN and the Firewire are on the same
"bracket" I wonder if there is a discontinuity on a common connection. If it
is a board problem I don't want to break it down even though it is under
warranty as I will be without it for who knows how long.
Barry
 
"Barry" said:
Thanks for that, I have another PC, I'll have to read your notes carefully.
The Firewire doesn't work either although I gather it is a bit sniffy on
these boards anyway. Since the LAN and the Firewire are on the same
"bracket" I wonder if there is a discontinuity on a common connection. If it
is a board problem I don't want to break it down even though it is under
warranty as I will be without it for who knows how long.
Barry
Click to expand...

If you want to replace the Ethernet with a 10/100 card, those
are dirt cheap. If you want to buy a 10/100/1000 card, those
are more expensive (for no good reason). An RMA could well be
cheaper than buying a 1000BT card.

According to the manual, the stacks are USB,USB,Firewire and
USB,USB,RJ45. I don't see a sharing there.

While the info is not going to help you, the Ethernet outputs
are transformer isolated. Generally, there is no DC path to
ground with respect to an Ethernet output wire. There is a black
plastic square labelled "Pulse H5007" next to the connector
stack, and that contains the four transformers used to isolate
the eight wires. With no DC path, it means two computers can
have slight differences in their ground potential, without
causing a problem. If electrical noise is imposed on the cable,
both wires in a pair "see" the same amount of noise, and the
noises cancel when they hit the transformer. Each pair is
differential (signals of opposite polarity), so the receiving
IC can eliminate any remaining common mode noise.

Pg.3 here shows how the four pairs of wires in the cable are
transformer isolated. This is what is inside the H5007 plastic
square, just before the wires go to the RJ-45. On some
motherboards, this plastic square is actually inside the
connector stack, but in this case, you have a better quality
solution, where the square is separate on the motherboard.
(Better, in the sense that the connector stack thing can
be lower quality.)

http://www.pulseeng.com/pdf/HC500.pdf

Pg.55 here shows how the transformer is connected to the
Ethernet chip. This info will only help you if you are
handy with an ohmmeter. It also shows the pin numbers in
the RJ-45, and how the pin numbering is not in a particularly
intuitive order.

http://download.intel.com/design/network/applnots/ap440.pdf

Paul
 
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