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From: mjg@ecsvax.UUCP (Michael Gingell)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Writing 360K diskettes on 1.2 Mb dri
Message-ID: <2441@ecsvax.UUCP>
Date: Mon, 8-Dec-86 08:50:46 EST
Article-I.D.: ecsvax.2441
Posted: Mon Dec  8 08:50:46 1986
Date-Received: Tue, 9-Dec-86 11:28:12 EST
References: <184138@<1986Oct26^> <2690002@hplsla.HP.COM>
Organization: UNC Educational Computing Service
Lines: 28
Summary: Never write using a 1.2 Meg drive to a floppy disk that has been previously formatted on a 360 K drive (without bulk erasing).

In article <2690002@hplsla.HP.COM>, davidr@hplsla.HP.COM (      David Reed) writes:
> By way of comment from my experience:  I have found with the great variety and
> numbers of computers I use around here that:
>     a 360K disc formatted in a 1.2M drive (with the /4 option to format as
>        a 360K disc, of course) canNOT be read in about 1/3 of the 360K 
>        drives when a 1.2M drive also writes the data to the disc, but
>     a 360K disc formatted in a 360K drive and written to by a 1.2M drive
>        can NEARLY always be read in a 360K drive.
> 


I would disagree with the above entirely. The above rules are either
accidentally reversed or a recipe for disaster.  Disks made on 360k
drives should NEVER be written to with a 1.2 Meg drive if you want
to subsequently be able to read them on a 360K drive again (unless you
bulk erase and start all over again).  WHen you
write to a 360K disk using a 1.2Meg drive the erase/record head cuts
a tunnel down the middle of the old 360K recording. This is fine as
long as you only ever play back the disk on 1.2M drives. However if
you try and read it on a 360K drive the head will pick up the 1.2Meg
recording PLUS the residual unrerased 360K recording on each side
resulting in a high probability of errors.

The cardinal rule is this: If you must use 1.2M drives to make 360K d
disks, make sure the disk is either new or bulk-erased, or that it has
only ever been written to by a 1.2M drive in 360K format. 

Mike Gingell     ....decvax!mcnc!ecsvax!mjg