PRECOMP

        Notes on bits 13-14: Precompensation


        These set the disk disk controller's precompensation
        time, which directly affects the density of the data
        written to disk.  The faster the precompensation
        time, the higher the density.  With AmigaDos,
        density is highest on the inside tracks, probably
        due to the fact that these is less physical space
        for these tracks.