slow Kilauea TCP throughput?

[Donasch, Ingo @ SDS]

I have a project where I would like to use the AMC405EX under Linux for
high speed data acquisition. I have the Kilauea board in the lab but
measured only 150Mbit/s TCP throughput (outbound) with iperf. I need
twice of that and actually expecting 3x higher bandwidth from that
architecture.
what is it that I'm missing?
can anybody confirm my results or tell me what am I doing wrong?
any help is appreciated
sincerely
ingo

/home # uname -a
Linux kilauea 2.6.23-g1dfaad37 #1 Wed Nov 21 07:15:18 CET 2007 ppc
unknown

home # ./iperf -c 192.168.1.249 -t60 -i1
------------------------------------------------------------
Client connecting to 192.168.1.249, TCP port 5001 TCP window size: 16.0
KByte (default)
------------------------------------------------------------
[  5] local 192.168.1.50 port 59035 connected with 192.168.1.249 port
5001
[  5]  0.0- 1.0 sec  16.6 MBytes    139 Mbits/sec
[  5]  1.0- 2.0 sec  16.6 MBytes    140 Mbits/sec
...
[  5] 58.0-59.0 sec  18.0 MBytes    151 Mbits/sec
[  5] 59.0-60.0 sec  18.0 MBytes    151 Mbits/sec
[  5]  0.0-60.0 sec  1.04 GBytes    148 Mbits/sec
/home # ifconfig
eth0      Link encap:Ethernet  HWaddr 00:06:4B:10:19:5B  
          inet addr:192.168.1.50  Bcast:192.168.1.255
Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:798928 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1634765 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:53947650 (51.4 MiB)  TX bytes:2341215308 (2.1 GiB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)


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