[realtek] rtl8139 problem

Donald Becker becker@scyld.com
Sat Aug 31 15:31:01 2002

On Sat, 31 Aug 2002, Roberto De Leo wrote:

> I have 2 Linux Boxes connected through a twisted class 5 cable.

Home-made or commercially made?

You likely have mis-paired the cable.  The pairing is not the obvious
1+2,3+4,5+6,7+8, it should be 1+2,3+6,4+5,7+8

> Here is my problem: when the NE2k was connected I could tranfer files
> from one PC to the other at the regular 10Mbps speed.
> Now that the cards are both 10/100 and so they could reach the nice
> speed of 100Mbps I get a much worse result: on the path 8129->8139
> I reach at most 1.4Kb/s [measured through a ncftp download], while
> on the opposite trajectory the trasfer speed does not pass .4Kb/s!!!

This sounds like corrupted packets.  You would get much higher speeds
even with a duplex mismatch.

> How can it be possible that the cards negotiate a 100Mbps speed but then
> behave so ridicolously bad?

Negotiation takes place at 10baseT speed, and even mis-paired cables
will work at that speed.

Donald Becker				becker@scyld.com
Scyld Computing Corporation		http://www.scyld.com
410 Severn Ave. Suite 210		Second Generation Beowulf Clusters
Annapolis MD 21403			410-990-9993