losing 100megabit and/or full duplex setup on nics

[Greg Lindahl]

> 1. TCP runs extremely slow, here is a netperf result

This is completely normal in the case where the switch and the card
disagree about half vs. full duplex.

You think udp is fine, but I'd bet that if you ping with 8000 byte
packets, you'll see horrible lossage.

> here is some diag info from one system using 3com card from vortex-diag
[...]
> Transceiver/media interfaces available:  100baseTx 10baseT.
> Transceiver type in use:  Autonegotiate.
> MAC settings: half-duplex.

Given that you forced the card to full-duplex, this bodes ill. You can
also probably query the switch to find out what it thinks the link is,
and I'll bet it says full duplex.

-- greg