On Mon, Dec 5, 2016 at 12:45 PM, Glen Slick <glen.slick at gmail.com> wrote: > But it also seemed to detect a sector number 17 with no data in each > track. Is that a normal 9121 low level format? > It's normal for the HP 3 1/2" floppies to have an extra sector, which is used for wear tracking, but I don't know about "no data".