The decoder memory bandwidth depends on frame rate, resolution, color depth, chroma format and Decoder profile. The LogiCORE IP provides an estimate of decoder bandwidth based on the video parameters selected in the GUI.
AMD recommends using the fastest DDR4 memory interface possible. Specifically, the 8x8-bit memory interface is more efficient than 4x16-bit memory interface because the x8 mode has four bank groups, whereas the x16 mode has only two and DDR4 allows for simultaneous bank group access. For more information, see AMD Answer: 71209.