Editing Modified frequency modulation (section)

==Data separator==
Because the MFM system requires more accurate timing of the clock signal, it was not possible economically to build the required analog and digital components on a single [[integrated circuit]] using late 1970s technology. Instead, MFM drivers required the drive vendor to design their own [[clock recovery]] circuitry, a system known as the '''data separator'''. Data separator design was an art form of its own.<ref>{{cite tech report |url=https://fliphtml5.com/pdlu/wfhr/basic |title=Floppy Disk Data Separator Design Guide for the DP8473 |first1=Bob |last1=Lutz |first2=Paolo |last2=Melloni |first3=Larry |last3=Wakeman |publisher=National Semiconductor |date=1982}}</ref>

Among the most widely used controllers of the era was the [[Western Digital FD1771]] series. The original FD1771 supported FM only, but it was quickly paired with the FD1781 and FD1791 which performed MFM based on an externally provided clock signal. Implementing MFM support with these drivers required an external data separator. Rapid improvement in [[Semiconductor device fabrication|IC manufacturing]] in the late 1970s and early 1980s led to the first low-cost all-in-one MFM drivers in the early 1980s. The WD2791 was the first to directly support MFM using an internal analog [[phase-locked loop]], but it required a number of simple external components to implement a complete system. The WD1770 was the first to implement a complete MFM solution in a single chip.