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

Ian Buckley ianb at ionconcepts.com
Thu Jul 16 19:15:20 EDT 2015


Paul,
It's important to understand that "Overflows" result from the inability of the host computer to keep up with the USRP.
The link you referenced is just a discussion of potential H/W bottlenecks in the USB3 controller…note the paragraph:
It is possible that performance will be impacted by other variables such as the operating system, processor, etc.  The rates shown in the table below are not guaranteed.

Ron's suggestion will likely help you greatly and you'll find more threads in the fairly recent past on the same topic.
-Ian

On Jul 16, 2015, at 4:02 PM, Ron Economos via USRP-users <usrp-users at lists.ettus.com> wrote:

> Increasing the buffering with num_recv_frames usually does the trick. Like so:
> 
> benchmark_rate --rx_otw sc16 --rx_rate 28000000 --args="master_clock_rate=56000000,num_recv_frames=128"
> 
> Ron
> 
> On 07/16/2015 02:03 PM, Paul Andrews via USRP-users wrote:
>> 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
>> 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?
>>  
>> Paul
>> ------------------------------------
>> 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
>> OO
>> 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
>>  
>>  
>> Done!
>> 
>> 
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>> USRP-users at lists.ettus.com
>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
> 
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