The X3 has a floppy drive and can load .KMP (KeyMap) and .K25) sample files. SysEx is generally not used to transfer actual audio samples due to the slow speed of MIDI. Samples are loaded via floppy disk (or HXC/Gotek emulators).
: The X3 is often compared to its "siblings," such as the Korg M1 (its predecessor) or the Korg N364 (which is effectively two X3s bundled together). Summary of "File" Interactions korg x3 sysex files