GNU Radio + Beagleboard Question

I’ve been trying to check the performance of GNU Radio running on the
Beagleboard and I was wondering if anyone has tried running the
benchmark_tx and/or benchmark_rx scripts on them. When I was running
benchmark_tx with dbpsk with symbol rate of 125k and a packet size of
1000 bytes the script would run but I would start getting “uU” messages
between packet transmssions until the script fails. When I reduced the
packet size to 100 I was getting less “uU” errors and the script would
not fail. I’m assuming that “uU” means USRP underflow and the error
would basically cause the beagleboard to throttle transmissions.

Has anyone tried this? Is the error caused by the beagleboard being too
slow at producing packets? In order to further explore the issue what
files should I look at?