From: Dr. David Kirkby (drkirkby@ntlworld.com)
Date: Sat Jul 26 2003 - 20:15:07 EDT
I've already summarised this once, but have a bit more information now
which others might find useful. The problem is now solved - at least
to my satisfaction.
As you may be aware, I've had poor reliability of an ethernet
connection between a Dec Alpha Personal Workstation 600au and my
switch, which is a 3COM 16-port OfficeConnect unit. This has now been
solved - see below.
The switch is what I would consider a home/small-office switch - there
is no ability to set auto/half/full duplex, it runs off an external
power supply ... etc. i.e. it's not exactly a 'professional product'.
When I bought the Alpha I tried setting the Alpha to full duplex in
SRM:
>>> set ewa0_mode FastFD
but that failed to achieve full-duplex, but instead worked at half
duplex (I don't know if it was reliable or not, as I never transferred
any data), but the switch showed it using half-duplex.
I've also tried setting the tulip to auto in SRM, which negotiates at
full-duplex with the switch, but is unreliable. That was the problem.
Thanks to Thomas P. Blinn, Bob Marcan, Peter Wolfe for additional
information.
Main points are:
1) Thomas Blinn has said the 'tulip' ethernet connection (as used on
the 600au) is very old and has undergone a number of revisions. He
can't tell me the exact bug fixes that have, or have not, been applied
to the tulip chip set I have without a lot of work. So it's difficult
to say exactly how good/bad my tulip is.
Thomas has said most issues seem to related to auto-negotiation, which
I am using, since setting full-duplex on the Alpha failed to give
full-duplex.
2) Bob Marcan said "I have the same problem with the cheap switch from
??? (don't remember the name). With Cisco, Enterasys and cheap LEVELA
switch works flawlessly."
3) Peter Wolfe felt me summary, which said:
> The general consensus of replies seems to be that the Tulip chipset
> used in the network connection of the Alpha is not very good and is
> not reliable in 100baseT full duplex.
was untrue and misleading, saying that to his knowledge they all work
fine in 100baseT full duplex, BUT the trick is to set this at both the
switch and in SRM. He admits not all versions auto-negotiate properly.
But I have no control over the switch.
4) It's been pointed out that there is a reasonably good probability
that a Intel
Etherexpress network card, will work reliably, as that is similar, if
not identical to the Dec DE600 network card, which everyone admits
works well. I think I have one such card around in a PC, or if not can
borrow one for test purposes.
THE SOLUTION:
My 'solution' was to force the network card to 100baseT half-duplex
with the command:
>>> set ewa0_mode Fast
So now my Alpha works (at least in the hour since I did it).
Previously it seemed impossible to transfer 2 Mb in under 2 minutes,
and very often it timed out, so I think there is a definite
improvement.
For the use the workstation gets put to, I don't need the performance
of full-duplex. I'd much rather a reliable half-duplex connection than
a totally unreliable full-duplex connection. As such, I'm not even
going to bother searching for a Dec DE600 or Intel Etherexpress card.
I'll leave it set to half duplex and worry about other things that are
more important to me! Even if I find a card here, I'm not going to
bother trying to configure it.
-- Dr. David Kirkby, Senior Research Fellow, Department of Medical Physics, University College London, 11-20 Capper St, London, WC1E 6JA. Tel: 020 7679 6408 Fax: 020 7679 6269 Internal telephone: ext 46408 e-mail davek@medphys.ucl.ac.uk
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