[USRP-users] X300 and UHD Converter

Serge Malo serge.malo at averna.com
Thu Apr 30 15:17:56 EDT 2015

Hi all,

I have a performance issue with my PC connected to a X300.
My Setup is: Windows 7 x64, X300 via 10GbE (intel X520-DA2), UHD 3.8.2

I was doing tests with the UHD benchmark_rate example, using both channels in Rx at 50Msps (100Msps in total)
I did not get any overflows when using the default parameters (rx_cpu = fc32).
However, when I use rx_cpu = sc16, I get overflows.

I looked into UHD, and found out that the converter from sc16_item32_be to fc32 is highly optimized (using SSE2), while sc16_item32_be to sc16 (little-endian) is not optimized. I'm pretty confident that the overflows happen because of this (my CPU is not fast enough for this version of the converter)

My goal is to record 16-bit samples in little-endian format.
I have a few questions:
-Is there a way for the X300 to send samples over 10GbE in little-endian format, in order to avoid conversion on the Host CPU?
-When using PCIe, can the X300 send samples in sc16_item32_le format otw?
-In TX, when the application has 16-bit little-endian samples, does conversion happen on the Host CPU too?

Best regards,
Serge Malo

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