for samba

when i copy files from samba share (usb 2.0 drive), speed is around 1 - 1.5MB/ sec. and this is very slow for fast drive.Other bottleneck does not exists.
Utilization of cpu is 100% ! Samba is about 90%.
Overclocking will be very helpful.
At least i need about 5MB/sec (i think that is impossible)
HW: Asus 500gx + USB HDD(WD 320GB, format xfs)