Serial NOR Flash Memory, MXSMIO (Multi-I/O), MX25/66xxx33/35/36/39 Series Macronix MXSMIO Family of Multi-I/O interface offers the 1.8 V, 3 V, and wide voltage range of Serial NOR Flash Memory products. The MX25/66xxx33/35/39 series, comes with a Multi-in / Multi-out interface, and quad Input/Output operation, which quadruples the read performance of systems.