< <But from my measurements, I think that it's very unlikely that a drive <can tell FM from MFM. I will try it sometime to confirm this. True, but the timing is still important. The SPEC I have for a Sony MP-F17W-70D (11/1988) makes it pretty clear that the acceptable rates are 250/500kBITS/Sec MFM with no discussion of plain FM. So it's probable the 8" SD rate of 250kbits/sec would work. The 5.25" floppy single density rate of 125kBITS/sec clearly would fall below the spec. There are limits to the write pulse width as well but I'd bet the 1771 meets them as they are fairly narrow range for all data rates and formats. Keep in mond most all of the floppies I know of do have a minimum due to the read amps bandwidth (there is a banpass filter!) and the differentiators used to recover the read data. the head gap width also sets the minimum data rate as well though to a lesser extent. The easiest was to see this is record a track at different rates from 50khz through 1mhz and look at what comes out (or not). Allison