Can get 10mbit/s but not 100mbit/s

[Sim]

I have 2 PC's on a LAN. One of them is a midi tower case a Realtek 8139, the
other is a micro-ATX with an onboard NVidia networking controller. I can
connect both PCs at 10mbit/s half duplex just fine but I cannot connect them
properly at 100mbit/s half duplex. I have even searched
PracticallyNetworked.com and found nothing that relates to this problem.

With the main PC using the Realtek 8139 we had an older PC ages ago on the
other end, also using an 8139. This worked fine at 100mbit/s half duplex, so
this rules out any physical problem

At the moment it is on 10mbit/s half duplex but I want 100mbit/s. How can I
sort this out?

Sim

 

[John Wunderlich]

I have 2 PC's on a LAN. One of them is a midi tower case a Realtek
8139, the other is a micro-ATX with an onboard NVidia networking
controller. I can connect both PCs at 10mbit/s half duplex just
fine but I cannot connect them properly at 100mbit/s half duplex.
I have even searched PracticallyNetworked.com and found nothing
that relates to this problem.

With the main PC using the Realtek 8139 we had an older PC ages
ago on the other end, also using an 8139. This worked fine at
100mbit/s half duplex, so this rules out any physical problem

At the moment it is on 10mbit/s half duplex but I want 100mbit/s.
How can I sort this out?

Need more information. How are the two computers connected?

Half-Duplex implies that they are connected through a hub. Does the
hub support 100-Base-T? By the time 100-Base-T became popular, hubs
were being replaced with switches so running with a hub at 100-Base-
T is unusual. If you have a router or switch connecting them, then
the proper setting is probably Full Duplex instead. Does the
router/hub support 100-Base-T?

100-Base-T is faster and also requires a higher quality cable
connection. Make sure that all your cabling is at least Cat 5 and
it is in good condition. Also make sure no cable runs are over 100
meters in length. If the RJ-45 connections at the cable ends are
home-made, make sure that the proper color wire is in the proper pin
-- correct twisted pair grouping must be maintained.

HTH,
John

 

[Sim]

Need more information. How are the two computers connected?

Both computers are directly connected with a crossover cable.

100-Base-T is faster and also requires a higher quality cable
connection. Make sure that all your cabling is at least Cat 5 and
it is in good condition. Also make sure no cable runs are over 100
meters in length.

Done that. If the Realtek 8139 works with the same card on the other PC,
then surely it must work with the NVidia network controller, but its not
working at 100Mbps.

Sim

 

[CJT]

Both computers are directly connected with a crossover cable.

You don't have 10 bucks for a switch?

 

[Sim]

You don't have 10 bucks for a switch?

I don't have a spare mains socket for a switch, never mind £5. I use all my
mains sockets for my music gear.

 

[CJT]

I don't have a spare mains socket for a switch, never mind £5. I use all my
mains sockets for my music gear.

What would be so awful about full duplex, then?

 

[John Wunderlich]

Both computers are directly connected with a crossover cable.

With a crossover cable and half-duplex, the NIC on the receiving end
won't echo back the traffic sent to it by the sending side (like a hub
would) so the sender doesn't see his own traffic on the line so he
thinks his packet was trounced. This results in aborted traffic and
constant retries and it probably will never succeed. Use Full Duplex
in this configuration.

HTH,
John

 

[Sim]

What would be so awful about full duplex, then?

Hardly any difference between half duplex and full duplex when it comes to
normal internet usage.

 

[Sim]

With a crossover cable and half-duplex, the NIC on the receiving end
won't echo back the traffic sent to it by the sending side (like a hub
would) so the sender doesn't see his own traffic on the line so he
thinks his packet was trounced. This results in aborted traffic and
constant retries and it probably will never succeed. Use Full Duplex
in this configuration.

I did set it to 100Mbps full duplex and it still won't work properly.

Sim

 

[CJT]

Hardly any difference between half duplex and full duplex when it comes to
normal internet usage.

So ... problem solved.

 

[CJT]

I did set it to 100Mbps full duplex and it still won't work properly.

Sim

Oops. Time for that switch. Run an extension cord if necessary,
or run it off batteries.

 

[Sim]

So ... problem solved.

Except I can't use 100Mbps on the LAN.

 

[CJT]

Except I can't use 100Mbps on the LAN.

I think your crossover cable is probably mucked up. That it works at 10
Mbps means (almost) nothing.

 

[Sim]

I think your crossover cable is probably mucked up. That it works at 10
Mbps means (almost) nothing.

Only when I try to get the RTL8139 and NVidia network controller
communicating.

 

[chrispsg]

There is a big difference between full duplex and half duplex
communication. Think of half duplex communicating by walkie talkie.
Only one device can transmit or recieve at one time. Full Duplex is
comparative to a telephone conversation both people can transmit and
recieve at the same time. I would try replacing the NIC that causes the
10 Mbps. Or buy a switch..