Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!dptg!att!mtuxo!gjp1
From: gjp1@mtuxo.att.com (XMRK4-G.PATEMAN)
Newsgroups: comp.sys.ibm.pc
Subject: Re: 3.5" High-Density Woes
Summary: Heed this warning!
Keywords: penny wise, pound foolish
Message-ID: <5221@mtuxo.att.com>
Date: 22 Aug 89 16:30:11 GMT
References: <1001@apctrc.UUCP>
Reply-To: gjp1@mtuxo.UUCP (XMRK4-G.PATEMAN)
Distribution: usa
Organization: AT&T, Middletown NJ
Lines: 40


In article <1001@apctrc.UUCP> zgel05@apctrc.trc.amoco.com 
(George E. Lehmann) writes:

>DON'T USE 3.5" DS/DD DISKETTES FOR HD (1.44MB) USAGE!!!!!

AND DON'T USE 5.25" DS/DD DISKETTES FOR HD (1.2MB) USAGE!!!!

OK, once more for those who still believe it's a cost-effective approach: 

When you format a low density (LD) disk in a high density (HD) drive, 
a large number of sectors will be marked as "bad".  They're not actually 
bad, of course.  It's just that the 300 Oersted magnetic coating of an LD
disk can't hold the signal the same way an HD's 600 Oe coating can.  Look 
at the two types side-by-side.  The HD disk has a noticeably darker coating.

Alright, so you've formatted the 360K at 1.2M and all the "bad" sectors have 
been marked.  You don't quite have 1.2M but you have a lot more than 360K.  
The problem is that many of the marginal sectors which read back successfully 
THIS TIME won't necessarily be readable later on when the disk contains your 
valuable data.  How likely is that, you ask?  VERY!  An associate of mine 
used LDs exclusively on his HD machine and found that more than half of them 
contained unreadable files.  When he tried to read them on another machine,
the situation was even worse.

If the read error occurs in a text file you might, with the help of the Norton
Utilities, Mace Utilities, etc, be able to piece it back together.  If it 
occurs in a binary file, you probably won't.  If it occurs in a critical area 
like a directory or the file allocation table, you can probably kiss most or 
all of the disk goodbye. 

    Is it really worth the difference in price between HD and LD media?

------------------------------------------------------------------------------
George J. Pateman
CAHTP Media Lab
AT&T / Bell Labs
Room 4D-333
200 Laurel Ave.
Middletown, NJ  07748