Re: SLOW 1 gbit LAN nforce 650i
Interesting... That at least gives you something to work with.
I'd bet that could be the issue then. If you're maxing out one core with that little bit of data then something is definitely wrong. My Althon XP 1800+ can move 40 - 50MBps (320 - 400mbits) before it runs out of CPU. That pc is using a Linksys gig card.
Here are some options you can test then.
Flow Control - Disabled
IP Checksum Offload
Large Send Offload V1
Large Send Offload V2
TCP Checksum Offload
UDP Checksum Offload
All of these are RX & TX enabled on mine.
Receive Side Scaling - Enabled
Those should be all of the default options.
Also, check the Jumbo Packet setting. It should be 1514 by default. If you have Jumbo Frames set on one pc and not on another, weird things can happen. It might also be possible that your switch doesn't support jumbo frames. If both are set to ~ 1500 you can try to up that value on both making sure they use the same value.