8139C problems

Hi there,

I seem to have a problem with the realtek drivers for the 8139C: I used
to have kernel 2.4.18 with the aforementioned cards, using 8139too. This
gave me sluggish network performance (nearly analog modem speed, around
5KB/s and sometimes up to 16 KB/s) and a high error count on the
receiving end. Mii-tool reported 10Mbit half-duplex on all machines.
When I tried the rtl8139 driver from www.scyld.com's netdrivers.tgz
package the performance went to an acceptable speed (~8MB/s depending on
application and CPU power available) and mii-tool reported 100Mbit/s
full-duplex on all machines (all equipped with the same card). So far so
good, but when transferring large amounts of data, like RH iso images,
the interface would stall and give up working. I had to restart the
interface.

Now, since I read that changes were made to the 8139too driver, I
installed kernel 2.4.20-pre7 (v.0.9.26 of 8139too) on one machine.
Mii-tool now still reports 100Mbit/s full-duplex on all machines (the
others are still running 2.4.18 with said rtl8139 from netdrivers.tgz),
but the performance is down to 5-16 KB/s with a high error count on the
receiving end. It doesn't matter which way I try to transfer or which
protocol I am using (scp, ftp). rtl8139 doesn't seem to work for me with
2.4.20-pre7, it loads, but I can't establish a connection.

Am I doing something really wrong?

Any pointers, hints and kicks to the head (metaphorically speaking) are
highly appreciated. Thanks in advance.

Regards
Andreas