eepro100 vs. ntulip speed

[Bob Edwards <Robert.Edwards@anu.edu.au>]

I have a lab of machines with Intel eepro 100+ adaptors all running
etherboot/netboot and a beowulf with Intel/DEC 21143-based adaptors
also running etherboot/netboot. In both cases the machines are loading
a 5.4MB boot image (compressed kernel + compressed initial RAM disk).

In the case of the eepro 100 machines, even on a relatively busy
network, I can get the image TFTP'd in about 3.6 seconds (= 1.5MBytes/sec)
which isn't too bad - clearly faster than 10Mbps but, not surprisingly,
not using anywhere near all of the 100Mbps available.

In the case of the 21143 based machines, even on a completely quiet
network, ntulip is taking over 42 seconds to load the same size file.

I have checked with tcpdump in both situations. In the case of the
eepro100's, the 516byte TFTP frames are sent out about once every
350usec (there are about 10,600 such frames). In the case of the
ntulip 21143's, the frames are sent out every 3900usec. It looks
suspiciously as though the 21143 is running about 1/10 as fast, and
yet, even at 10Mbps, a 516 byte frame should only take about 440usec,
plus, the managed switch assures me that it is connected to the 21143
card at 100Mbps Full Duplex during the 42 second download.

Once Linux is up and running, I am getting a little over 8MByte/sec
NFS from the 21143 card, which is about as good as you can expect
from NFS across a 100Mbps full duplex link, so that indicates that the
card itself is not the problem.

Anyone got any idea as to why the eepro100 driver is so much faster at
the TFTP than the ntulip driver? I have tried playing with UADJUST and
other timing related variables, with no positive effect, and usually
the negative effect of causing the TFTP to hang up.

Any help or suggestions would be much appreciated.

Cheers,

Bob Edwards.
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