https://kb.ettus.com/About_USRP_Bandwidths_and_Sampling_Rates
Host Bandwidth
The host interface allows data to stream between the FPGA of a USRP device, and a host PC. Most applications stream I/Q data to and from the USRP device. A summary of the various interface options that are available with the USRP product line are shown below. The host sample rate with 16-bit I&Q samples are shown. Most USRP models also provide to option to stream 8-bit samples, effectively doubling the host-bandwidth in terms of samples/second.
In this context, “full duplex” means that the interface can stream in both directions at the specified rates simultaneously. Some interfaces, such as USB 3.0, do not provide separate data paths for transmit and receive data, but reuse a single transport in a “half duplex” mode. In this case, the total interface bandwidth would be shared between the transmit and receive functions of a USRP.
It is important to meet filtering and bandwidth requirements to avoid aliasing. The extended bandwidth WBX-120, CBX-120 and SBX-120 daughterboards were design to work with USRP X300/X310 and any future products with sufficient ADC/DAC sample rates. These boards are not compatible with devices that incorporate lower rate ADC/DAC below 200 MS/s. See “Daughterboard Compatibility” for more information.