I'll add just a bit with respect to floppy disks on an MCU. One reason to put histogram and peak-detection in the MCU firmware is that for a disk you never know how far out of alignment the original (recording) drive might be. A drive used to record something out of alignment can yield garbage on a blind capture.
A drive that allows for adjustment means that you can sample a track, and adjust until you see nice clean peaks. Blind-on-the-fly recovery makes this a lot more difficult. You can certainly add some primitive decoding for FM, MFM, MMFM and a few varieties of GCR as a sanity check, but looking at spectral peaks is a first-line diagnostic. --Chuck
