[USRP-users] Bound in streaming X310 through PCIE

Marcus D. Leech mleech at ripnet.com
Wed Mar 9 13:45:09 EST 2016


On 03/09/2016 01:40 PM, Raj Bhattacharjea via USRP-users wrote:
> This is not exactly a comment on PCIE, but is relevant to high-speed 
> acquisition and processing with the X310. I have been able to get 400 
> MSamp/s from two X310s into a single host PC using 10GigE. Here is one 
> setup I'm using:
>
> Dual Xeons (E5-2600 Quad core @ 3.5GHz) running Xubuntu -> Intel 
> X520-DA2 -> 2 X310s
>
> I am able to get the full 400 MSamp/s without dropping samples into 
> the host PC and do spectrum/waterfall plots in gnuradio (uhd_fft or 
> osmocom_fft). There has been lots of discussion on this list about the 
> relative merits of PCIe vs. 10 GigE for the X310; your experience 
> compared to mine seems to serve as another data point in favor of the 
> consensus on this list, which is that 10 GigE is currently the 
> preferred interface for the X310, at least until the NI PCIe drivers 
> are as mature as the Intel 10 GigE drivers.
>
> -- 
> Raj Bhattacharjea, PhD
> Georgia Tech Research Institute
> Information and Communications Laboratory
> http://www.prism.gatech.edu/~rb288/ 
> <http://www.prism.gatech.edu/%7Erb288/>
> 404.407.6622
>
This is also an indicator that "much depends on what you're doing".   
Theuhd_fft and osmocom_fft programs use the FFT sinks from
   Gnu Radio, which implement a "stuttered" FFT implementation, which 
means that they only do as many FFTs as is required to achieve
   the configured frame rate, which is typically about 15 frames/sec.   
Which means that an overwhelming majority of your data are
   completely ignored...



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