I'm seeing an odd thing with the e100 driver.  It seems to be this way
with the 2.4 series and with 2.5.68, and I couldn't find anything with a
search.

I've attached a small program to measure latency of round-trip time on
UDP.  If I send 85-byte packets between two of my machines, I get 170us
round-trip latency.  If I send 86-byte packets, I get 1329us latency. 
This seems quite odd.  If I test on the eepro100 driver, I get expected
linear increase in round-trip time as the packet size increases, and it
never gets close to 1300us.

To run the program, do:

./ip_lat -s <port>

on one machine to run the server, and then do

./ip_lat <server IP> <port> 1000 85

to send 1000 85-byte packets from another machine.  Change the 85 to 86
to see the latency go up.

-Corey