Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!rochester!cornell!uw-beaver!tektronix!tekcrl!tekgvs!keithe
From: keithe@tekgvs.LABS.TEK.COM (Keith Ericson)
Newsgroups: comp.sys.ibm.pc
Subject: Re: 1.2meg/360k compatibility question
Message-ID: <5560@tekgvs.LABS.TEK.COM>
Date: 12 Jul 89 20:43:07 GMT
References: <IYiAOwy00UhBI1IEMx@andrew.cmu.edu> <1567@westmark.UUCP>
Reply-To: keithe@tekgvs.LABS.TEK.COM (Keith Ericson)
Organization: Tektronix, Inc., Beaverton,  OR.
Lines: 65

In article <1567@westmark.UUCP> dave@westmark.UUCP (Dave Levenson) writes:
>
>	We sell software and support customer sites who use a mix of
>XT- and AT-class machines.  Originally, we used only a 1.2 Mbyte
>diskette drive, and formatted HD and DD diskettes diskettes in it
>for distribution.
>
>	What we found was that if we bulk-erased the media before
>formatting it, we could reliably read the DD diskettes that we
>formatted on the HD drive.  If we attempted to format the DD
>diskettes which had previously been formatted on a true DD drive,
>without bulk-erasing them first, we had occasional GENERAL FAILURE
>READING DRIVE A: troubles in the field.
>
>	The real problem, however, was when we took one of these
>"cross-formatted" diskettes into the field and tried to add one file
>to it by writing on it using a true DD drive.  That would almost
>always foul it up and make it unreadable on both DD and HD drives.
>
>	We have now installed both DD and HD diskette drives in our
>development machines, so that we can reliably send diskettes to the
>field and collect information and bring them back!
>

---------------------------------------------------------------------------
     
     Data track of a bulk erased diskette:
     
     !@#$!@#$!@#$!@#%#@$%^$()%^&%^(^&*()&*)*(&)(%^&%&%$#@
(1)  (&*()%^&%^^@#$#@!%#%^&(&*()*()_%$%#!@%$*^&)(*(&@#!%$
     !@#$@#%^$%^*^&(*&*)(&*(%$#%@#$%^#$^&%*^&*(&*)*(&_)(*
     
---------------------------------------------------------------------------
     Data Track of a 360K-drive formatted diskette:
     
     ####################################################
(2)  ####################################################
     ####################################################
     
---------------------------------------------------------------------------
     
     Data Track of a 360K-drive-formatted diskette WRITTEN with a 360K drive:
     
     1234567890123456789012345678901234567890123456789012  \
(3)  1234567890123456789012345678901234567890123456789012   >---data
     1234567890123456789012345678901234567890123456789012  /
     
---------------------------------------------------------------------------
     
     The above Data Track WRITTEN with a 1.2M diskette:
     
     1234567890123456789012345678901234567890123456789012
(4)  ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ  <--data
     1234567890123456789012345678901234567890123456789012
     
---------------------------------------------------------------------------
     
Now - guess what kind of problems the 360k-drive is going to have when it
tries to read track (4).

A(nother) 1.2M drive (assuming it's properly aligned) WILL be able to read
track (4).

     
kEITHe