On Oct 13,  8:34, allisonp(a)world.std.com wrote:
  I know when NS* offered
 the DD controller one option was 96tpi twosided drives and it was called
 quad density as it was 800k and the same controller single density on
 a 35track single sided (the introductory format) was a whopping 90k! 
I remember *them* well.  And I remember the awe at getting Apple DOS 3.3
140K on the same drive (well, same SS 35 tracks, anyway).
--
Pete                                            Peter Turnbull
                                                Dept. of Computer Science
                                                University of York