RE: Multia UDB Hardware Questions

Shane Anderson (
Tue, 19 Nov 1996 19:03:05 -0500

On 19 Nov 96 at 15:31, Steven W. Decato wrote:

> Our tests involved 2 Pentium 100 machines running Linux 2.10 wired directly to
> each other via a crossover cable (send->receive, receive->send) "point-to-point".
> Using the crossover cable, no other machines are on the network, so traffic is
> not a consideration. We used 3COM595 100BT cards PCI cards. The software simply
> transmitted packets of various sizes and measured performance. We tested using
> straight sockets and MPI. Our tests revealed a maximum throughput of 2.5 megabytes
> per second. However, we noted that CPU load was nearly 100% so the assumption is
> that the process is CPU bound. We will do more testing to determine if a faster
> CPU will give faster performance. If so, how much faster? We also have a dual
> Pentium machine we will be doing testing on. Another variable to consider is the
> card itself. PC magazine noted in a recent article that the 595 cards do have a
> tendency to load down the CPU. I suspect this is why 3COM is now selling the
> Etherlink XL 10/100 cards (3COM-905TX).

I believe Alan Cox detailed the difference between the 3COM and DEC
PCI ethernets. If I recall correctly, the 3COM is bus-mastering but
the memory range was so limited (for DMA) that it was a real hassle
to keep packets moving--lots of CPU intervention... The DEC chip
21140 or whatever (and the other DEC chips) didn't have these
limitations so back to back packets were a lot easier and less CPU

But I'm no expert and maybe some of the newer 3COMs don't have the
same problems... Check the Linux Networking pages for more accurate

=Shane Anderson===========Nonvolatile Electronics, Inc.===
E-Mail: Work Phone: (612) 996-1618

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