From: uhclemLOSE.feb06@nemesis.lonestar.org   
      
   Homer J Simpson  wrote:   
   : I wonder if 'dd' can be used to copy 8" floppy disks to 3.5" floppy disks in   
   : order to migrate the software to image files? Or could one dd the boot and   
   : the balance (separately) to the HD, and then use tar to copy those files to   
   : a PC style disk?   
      
   No.  The 3.5" HD media normally has the wrong number of sectors per track,   
   so a straight dd would not place sectors in the right places on the media   
   when copied from 8" media, at least if a real disk controller or   
   accurate emulation is being used.   
      
   Only 5.25" HD media allows this direct substitution and two dd does work   
   for 8"=5.25" media, one to copy the SD track and one to copy the rest.   
      
   In theory, 3.5 HD media can be "under-formatted", with only 16 sectors   
   per 512 byte sector per track, but a special formatter would have to be   
   used to make one, and you still have replicate the SD track as well.   
      
   For my own migration purposes, I made a special version of z80ctl that   
   directly supports 3.5" HD 18 sector media and 5.25" HD 15 sector media   
   (both PC compatible), and ported a copy of XENIX tar over to FreeBSD.   
   GNU tar works okay except for large files that span floppies, where the   
   XENIX tar is needed.  (Some day when I run out of things to do, I'll   
   make these pieces available.)   
      
      
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