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From: rap@oliven.UUCP (Robert A. Pease)
Newsgroups: net.micro
Subject: Re: Erasing Disks
Message-ID: <830@oliven.UUCP>
Date: Tue, 19-Mar-85 17:46:31 EST
Article-I.D.: oliven.830
Posted: Tue Mar 19 17:46:31 1985
Date-Received: Thu, 21-Mar-85 03:53:50 EST
References: <1960@sdcc6.UUCP> <736@ihnp4.UUCP>
Organization: Olivetti ATC, Cupertino, Ca
Lines: 30

.

>It is funny that you mention this.  Last night I was talking with a DEC
>c.e. concerning floppy disks on a PDP 11/23+.  One of the comments that
>he made was that if a bulk eraser is used on a floppy for that system,
>servo (head) positioning data is lost on the floppy, and the disk is
>totally useless.  There is no field program to reformat that part of the
>disk, at least according to him.  I have no reason to doubt him.
>
>Of course, we were talking about one specific system, and one type of
>drive (the RX02).  These comments may not apply to a 5 1/4 inch drive
>on a PC, but do you want to experiment?
>
>					jeff williams
>					AT&T Bell Laboratories
>					Naperville, Ill.
>					ihnp4!cfiaime

This is totally true.  The RX02  uses  track  address  marks
that are formated single density and the sector ids and data
blocks are  formated  double  density.  The  format  program
under  RT-11  passed  over  the  track  addresses  and  only
formated the sector ids and data fields.  If we ever  needed
to  format  a totally munched disk we formated it on our MDS
workstation and then reformated on  the  PDP.  What  a  pain
that was at times.
-- 

					Robert A. Pease
    {hplabs|zehntel|fortune|ios|tolerant|allegra|tymix}!oliveb!oliven!rap