USRP X440 cannot upgrade to FPGA CG_400 and CG_1600 and underflow at 100MHz.

[BIXUT]

Hi, I am using USRP X440 and a host PC with i9-14900K. I am using NVIDIA Mellanox MCX516A-CCAT ConnectX®-5 EN Network Interface Card (100GbE Dual-Port QSFP28, PCIe3.0 x 16) for connection and run on Ubuntu 24.04. When I tried to test the maximum bandwidth in GNU Radio, I find that it underflows at 100MHz with only transmitting a cosine wave signal in one channel (CPU usage is not closed to 100%). For this, I am using FPGA X4_200. I want to turn to FPGA CG_400 or CG1600 to try. However, when I do this, it said RuntimeError: Failure to create rfnoc_graph. The more detailed error screenshots are attached.

Do you have any idea about the underflow problem and the FPGA problem? Is that something wrong with the PC or the connection?

[GDEV · Accepted solution]

Hi Bixut,

the screenshots contain warnings that are related to streaming performance. Please apply the recommended system changes to raise allocatable memory for network interfaces.

Regarding the RFNoC failures, based on the fact that you are testing a 100MHz BW signal I suspect you are utilizing the DDC included in the X4_200 FPGA image. The 100GbE capable FPGA images CG_400 and CG_1600 FPGA images do not contain a DDC (or DUC), see also https://uhd.readthedocs.io/en/latest/page_usrp_x4xx.html#x4xx_updating_fpga_types. The error is then caused by UHD attempting to connect a RFNoC block (DDC) that is not available in the FPGA. To fix this you need to remove the DDC from your GR flow graph and be aware that your IQ rate is fixed (determined by the FPGA image).

Regards,