>                                loopback        Sun 4/600       Dec 5000/240
>        486/100/NetBSD 1.0      2.5MB/sec       650KB/s         950KB/s

That looks much better!

> Looks like with decent "other side" you can get close to 1MB/s off the
> card but this box is never going to drive FDDI wire speed... (assuming
> ttcp to localhost doesn't touch the NE2100 hardware)

Yup, ttcp to localhost loops back at the IP layer.  FDDI
bandwidth throughput should be possible on a PCI box with
changes such as minimizing data copying, larger device
queues and busmastering controllers with some onboard
intelligence.  Copying can be a pretty major cost: if you
have to move data even once, there goes 25MB/s of bus
bandwidth.  (With ethernet the cost of moving data one extra
time while achieving full bandwidth is *only* 2.35MB/s!)
This will result in a pretty busy cpu.

Bakul