Bad NICs

Paul Sherwin psherwin at
Wed May 12 21:57:35 GMT 1999

Steve Arnold wrote:
[Lots of bad performance stats for Realtek PCI ethernet cards]
> I guess I just don't have a head for business; why anyone would 
> want to buy or sell a deficient piece of hardware just because it 
> costs a few percent less, as opposed to a product that ACTUALLY 
> WORKS for just a few bucks more, is beyond my meager comprehension. 
Steve's tests are interesting and I'm not saying he's wrong, but you can
get some very strange performance variations moving big chunks of data
between a slow and fast computer. This is caused by the underlying TCP link
protocol trying to flow control the data stream - basically, the TCP window
size drops right down and the slow computer is only receiving a tiny data
chunk before sending an ack. This causes huge protocol overhead and the
data rate falls through the floor. I suspect a number of the reported
performance problems in this list are related to this - people tend to
stick Linux and Samba on an old 486 then use this to serve an office full
of brand new PIIs running WNT.

Why the performance figures for the 3c509 were so much better I haven't a
clue, unless the fact that it was an ISA card slowed the data rate
sufficiently to minimise the windowing problem?

Best regards, Paul

Paul Sherwin Consulting    22 Monmouth Road, Oxford OX1 4TD, UK
Phone +44 (0)1865 721438  
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