I am using an X310 with a custom daughterboard. The daughterboard is expecting the X310 to use the 120 MHz clock speed. The daughterboard is hardware defined to accept a 120 MHz signal to create an internal 60 MHz clock. The daughterboard upconverts a low IF signal to 60 MHz. The X310 is setup with a center frequency of 60 MHz and a sample rate of 4 MHz.