[comp.sys.mac] Formatting 800K disks in FDHD drives

costin@cogsci.ucsd.EDU (Dan Costin) (04/13/90)

How does one format a disk in an FDHD drive so it can be read by an
800K drive?  800K drives will format either 800K or 400K, for
backward compatibility.  Do 1.4M drives have no backward compatibility?

-dan

rc3h+@andrew.cmu.edu (Ross Ward Comer) (04/13/90)

Apple's FDHD drive automatically checks which type of disk is in the
drive and selects the proper format based on the disk type.  The HD
disks all have an extra hole opposite the lock-hole.  If you insert a
disk without that extra hole into an FDHD drive, the Mac will
automatically treat it as an 800K disk.

When the Mac asks if you wish to format a disk, it asks if you wish to
format single or double-sided.  Selecting double will give you 1.4M or
800K.  Selecting single on a non-HD disk will format it as 400K.

What this all means is that the FDHD is completely backwords
compatible with Apple's previous drives.  You simply need to use the
right disk type to determine the format used.  And it's incredibly
easy to tell which disks are HD when you buy them ;-).


ross

rc3h@andrew.cmu.edu
Carnegie Mellon University

Leo.Bores@f14.n114.z1.fidonet.org (Leo Bores) (04/14/90)

In an article of <12 Apr 90 17:19:47 GMT>, costin@cogsci.ucsd.EDU (Dan Costin) 
writes:

 DC>How does one format a disk in an FDHD drive so it can be read by an
 DC>800K drive?  800K drives will format either 800K or 400K, for
 DC>backward compatibility.  Do 1.4M drives have no backward compatibility?

Simply putting an 800K floppy into the drive activates the copy program to 
initialize it as either double or single sided (800-400K). Putting a 1.4M 
floppy into an 800K drive gets you (sometimes) an 800K disk that can no longer 
be re-formatted to 1.4M.

Leo Bores, M.D.





--  
Uucp: ...{gatech,ames,rutgers}!ncar!asuvax!stjhmc!14!Leo.Bores
Internet: Leo.Bores@f14.n114.z1.fidonet.org