[USRP-users] Unable to get samples above 14Msps with the B2x0 and USB3.0

Paul Andrews pandrews12 at sbcglobal.net
Thu Jul 16 17:03:35 EDT 2015

Dear USRP users,
I am trying to stream data from the USRP-B200, and I’ve noticed that I start getting overflows if I exceed a IQ sample rate around 16Msps.
I am using Window 8.1 Pro computer (Intel i7-4700Q @ 2.4GHz), and USB3.0 (with the Intel Series 8 C220 controller).
According to the information at: http://www.ettus.com/kb/detail/usrp-b200-and-b210-usb-30-streaming-rate-benchmarks <http://www.ettus.com/kb/detail/usrp-b200-and-b210-usb-30-streaming-rate-benchmarks>
I would expect to be able to data at 56Msps.   But,  I am getting much less than that.  Below are the results of the benchmark_rate at 28Msps, which results in overflows.
The maximum rate I can operate at is around 14Msps.
Any ideas how to resolve this issue?
C:\Program Files\UHD\lib\uhd\examples> benchmark_rate --rx_otw sc16 --rx_rate 28000000 --args="master_clock_rate=56000000"
Win32; Microsoft Visual C++ version 12.0; Boost_105600; UHD_003.008.003-release
Creating the usrp device with: master_clock_rate=56000000...
-- Operating over USB 3.
-- Initialize CODEC control...
-- Initialize Radio control...
-- Performing register loopback test... pass
-- Performing CODEC loopback test... pass
-- Asking for clock rate 56.000000 MHz
-- Actually got clock rate 56.000000 MHz
-- Performing timer loopback test... pass
Using Device: Single USRP:
  Device: B-Series Device
  Mboard 0: B200
  RX Channel: 0
    RX DSP: 0
    RX Dboard: A
    RX Subdev: FE-RX2
  TX Channel: 0
    TX DSP: 0
    TX Dboard: A
    TX Subdev: FE-TX2
Testing receive rate 28.000000 Msps on 1 channels
Benchmark rate summary:
  Num received samples:    279460546
  Num dropped samples:     201560
  Num overflows detected:  2
  Num transmitted samples: 0
  Num sequence errors:     0
  Num underflows detected: 0
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