High CPU load when copying files over network

Hiya,

I've just installed the Win7 RC on my lab-pc. It's a 2,4GHz Celeron, 1GB DDR-RAM, everything installend on some old 160GB PATA-HDD. Two hi-speed USB Keys are used for ReadyBoost (love that feature).

Everything works like a charm, except the file transfer from my WXP machine.

I mount the SMB share (which is on my WXP) from the W7 machine and start to copy some big files. Transfer speed is ~1MB/sec on 10MBit, ~5MB/sec on 100MBit and ~11MB/sec on 1GBit. When I start file transfer the CPU load pops up to 50% while 10MBit is active, for 100 and 1000MBit it jumps to 100% and stays there until the transfer is over.

Since I read about IRQ issues I tried some NICs. An onboard SiS-900, an RTL8139 based PCI card and an Intel Pro 1000/MT Desktop adapter. I thought that - at last - the Intel NIC should stop my problems as it comes with IRQ moderation and TCP/UDP checksum offload.

None of these 3 NICs solved my problem.

All these NICs run on the driver W7 has found for them. None of the vendors had a special driver for me.

What I tried to do in addition:

- disable W7 firewall
- disable IPv6
- disable QoS
- tried another CAT5e cable
- restart the switch (Netgear GS108)
- hit the whole machine

Note of the above worked.

I just hope you just have an idea left for me. Just ask if I missed out some details.