if any pair of pulses should be separated by either 2, 3, or 4 microseconds, a conventional drive might try to classify anything between 2.5 and 3.5 as 3, but if a track has two consecutive pulse intervals that are 2.4 and 2.6 microseconds long, while all other intervals are either less than 2.2 or greater than 2.8, recovery software might be able to conclude that particular edge is misplaced, and use the block checksum to determine what it should have been). I don't know how well the decoding software can deal with data errors (e.g. I've read of hobby projects to construct such things, but I don't know of any that would be practically usable outside the hands of data recovery services.Īs a compromise, there are some devices which interface with conventional floppy drives but precisely capture the timing pulses received from them. It one has a floppy drive which has been modified to feed the drive-head signal as an analog output, and allows finer-than-usual control over drive head motion, it may be possible to extract data from disks that cannot be read via normal means. As such, it must instantly decide whether each pulse is large enough to be detected, or should be rejected as noise, before it has a chance to observe anything beyond it. The PC floppy drive hardware is designed to convert sequences of pulses received from the drive head into a data stream in real time.
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