NOR-based flash has lower density than newer NAND-based systems, and CompactFlash is therefore the physically largest of the three memory card formats introduced in the early 1990s, being derived from the JEIDA/PCMCIA Memory Card formats. The other two are Miniature Card (MiniCard) and SmartMedia (SSFDC). However, CF did switch to NAND type memory later. The IBM Microdrive format, later made by Hitachi, implements the CF Type II interface, but is a hard disk drive (HDD) as opposed to solid-state memory. Seagate also made CF HDDs.