I have A7N266-VM and I also experience the bad performance with the 261 drivers. For additional information it might be caused by bad interrupt handling. While I use scp, vmstat -n 1 says the system uses about 130000 interrupts / s. The idle usage is 100 interrupts/s. The CPU usage is around 50%. The transfer rate is about 1MB/s.
With optimization=1 the interrupts drop to 65k/s and the transfer rate is 3MB/s. CPU utilization is ~55%.
I'm using Debian sarge with 2.4.24 kernel with debian patches.
On the other machine (dual P2 with realtek) there are only about 2500 interrupts /s on the same data rate. It uses 99% of the other CPU.
Next I'll try the 256 drivers.
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