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From: bill@bilver.uucp (Bill Vermillion)
Newsgroups: comp.sys.ibm.pc.hardware,comp.multimedia,comp.misc,connect.audit
Subject: Re: Diffs between DD & HD disks
Message-ID: <1991Apr12.182801.13714@bilver.uucp>
Date: 12 Apr 91 18:28:01 GMT
References: <1991Apr9.075828.2135@ibmpcug.co.uk> <1991Apr10.075541.638@kessner.denver.co.us>
Organization: W. J. Vermillion - Winter Park, FL
Lines: 21

In article <1991Apr10.075541.638@kessner.denver.co.us> david@kessner.denver.co.us (David Kessner) writes:
>In article <1991Apr9.075828.2135@ibmpcug.co.uk> hdrw@ibmpcug.co.uk (Howard Winter) writes:
>>BTW I understand the medium used in DD vs HD disks IS different,
>>and that the coercivity (the ease with which magnetism becomes
>>permanent) is the variable.  I have certainly never been able to
>>reformat an HD 3.5" to 1.44 once it has been formatted at 720,
>>and I believe that the switching of strength of magnetism used
>>is the reason  -  the weaker HD field cannot overcome the 720.

The reason you can't reformat to 1.44 is that the system checks the density
of the disk IF IT HAS BEEN PREVIOUSLY WRITTEN UPON.  Bulk erase it and it
will work just fine.

The HD format current requirements will EASILY overwrite anything that DD
writes.  But you first have to let the machine know that the disk IS blank,
and only a bulk eraser can do that.


-- 
Bill Vermillion - UUCP: uunet!tarpit!bilver!bill
                      : bill@bilver.UUCP