problem with Marwell gigabit performance

[OxY]

hi!

i have a Marwell (SMC) gigabit ethernet card (sk0) and 
have serious problems with performance..
the machine is a pc, amd 2000+ xp, 512mb ram.

tested with iperf (bidirectional test, udp transfer, not stream)
and got 8-15% packet drop when the system was idle.

then tuned the sysctl with these settings:

kern.ipc.maxsockbuf=81920000
kern.ipc.nmbclusters=5000000000
kern.ipc.somaxconn=8192
net.inet.tcp.inflight.enable=1
net.inet.raw.recvspace=4096
net.inet.tcp.recvspace=131072
kern.ipc.shmmax=409600000

with these i got around 3-7% packet drop,
but it's very high compared to zero :)

my question is where/what should i optimize to not
have packet drop at all, or at least reduce it as much as
possible.

thanks for your help!

Csaba Banhalmi, HU