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From: rcook@ircsun1.ccmblab.nd.edu (Robert Kelley Cook)
Newsgroups: comp.sys.mac.system
Subject: Re: HD disks failing at 800K format
Message-ID: <1991Apr10.204450.8125@news.nd.edu>
Date: 10 Apr 91 20:44:50 GMT
Article-I.D.: news.1991Apr10.204450.8125
References: <56990001@hpindwa.cup.hp.com> <1991Apr10.160835.5153@dartvax.dartmouth.edu>
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In article <1991Apr10.160835.5153@dartvax.dartmouth.edu>, Charles.E.Dubuque@dartmouth.edu (Charles E. Dubuque) writes:
|> 
|> Since HD disks have to store about 2 times as much information in the
|> same surface area, I would imagine that: 1) the HD drive writes a
|> signal that is of lesser strength than an 800K disk, otherwise it would
|> destroy data. 2) that the HD disks are of a more sensitive medium than
|> 800K disks, since it needs that extra sensitivity to pick up the weaker
|> signal.
|> 
. . . 
|> 
|> All this adds up to the problems you describe.
|> 
|> Moral of the story: never use HD disks in 800K drives. It isn't meant
|> to work that way (notice that Apple doesn't give you the option of
|> formatting HD disks ar 400K,800K or 1.4M)
|> 
|> Chuck


Actually, A high density disk needs a greater signal to flip the particles,
because the medium used is magnetically less susceptible to spurious changes.
They won't let you format high densitys as low density disks, because a low 
density drive doesn't nessecarily have the oomph to flip the bits of a high
density disk even though it can read them.

Robert Kelley Cook
U. of Notre Dame '91