Poor throughput

After I purchased my fifth TP-Link product with the NIC, I was disappointed for the first time:
A built-in Debian will only work with drivers, non-Plug and Play; This is, however, to the open source policy by Debian.
An Ubuntu 11.10 server recognizes the network interface card properly.
However, the data throughput is below ground (as measured by iperf):
Approximately 65 MB / s I reached in a simple network (Cat7 cable).
The Realtek Onboard Controller managed scarce 100 MB / s and an Intel controller (though PCIe) another 10 MB / s more.
Whether this is due to the PCI slot I can not judge, should theoretically possible bandwidth of the PCI bus of 133Mbyte / s, can ausreizen the network.
Another point of failure could be a faulty Linux driver.

I can not recommend the TP-Link network card a Linux user. Here I would rather advise to an Intel NIC.