USRP X440 underflow and cmd errors

[BIXUT]

Hi,

I am using USRP X440 and a host PC equipped with i914900K, connected through Mellanox dual 100GbE port network card and QSFP28 cables. I tried to use FPGA CG_400 and GNU Radio to test one transmit channel and one receive channel at the same time with a sample rate of 125MHz, but I noticed there is underflow even if my CPU usage is low. I downgraded the FPGA to X4_200 and want to see what is the maximum sample rate it can reach without underflow. I tried a sample rate of 50MHz and two transmit channels and two receive channels work at the same time, and I noticed that there is not only underflow, but also cmd errors. I would like to ask you what is the reason of this problem, because I think USRP X440 should reach a sample rate much higher than this.

Thank you very much for your help.

[BIXUT]

I also got a Control operation timed out waiting for ACK error that cause a stop.

[GDEV]

Hi BIXUT,

I recommend you start with using the UHD example rx_samples_to_file or rx_to_file.py. Do these errors reproduce with the example as well?

I can also recommend the "Benchmarking your system" in Ettus KB "Verifying the Operation of the USRP Using UHD and GNU Radio" to verify the capabilities of your system. You may also checkout Ettus KB "USRP Host Performance Tuning Tips and Tricks".

Regards