2-514: The FD1771 , sometimes WD1771 , is a floppy disk controller chip, the first in a line of floppy disk controllers produced by Western Digital . It uses single density FM encoding introduced in the IBM 3740 . Later models in the series added support for MFM encoding and increasingly added onboard circuitry that formerly had to be implemented in external components. Originally packaged as 40-pin dual in-line package (DIP) format, later models moved to
4-516: A 28-pin format that further lowered implementation costs. The FD1771 was succeeded by many derivatives that were mostly software-compatible: Many compatible chips were available from other vendors: These were used in many microcomputers including the TRS-80 , Acorn Electron , BBC Master , Atari ST , Acorn Archimedes , and the SAM Coupé , as well as the +D and DISCiPLE disk interfaces for
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