UPD765A - Single / Double Density Floppy-Disk Controller
The uPD765A/B is an LSI floppy disk controller (FDC) chip which contains the circuitry and control functions for interfacing a processor to 4 floppy disk drives.
It is capableof either IBM 3740singledensity format (FM), or IBM System 34 double density format (MFM) including double-sided recording.