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From: johnj@hijg.prl.philips.nl (John Janssen)
Newsgroups: comp.sys.atari.st.tech
Subject: HD and DD floppies (Was: FTP problems)
Keywords: HD and DD floppies
Message-ID: <2631@prles2.prl.philips.nl>
Date: 25 Mar 91 13:44:17 GMT
References: <X103y1w163w@bluemoon.uucp>
Sender: news@prles2.prl.philips.nl
Reply-To: johnj@idms.prl.philips.nl (John Janssen)
Organization: Philips Research Laboratories, the Netherlands
Lines: 60

I can not solve your FTP problem, but I have some 'news'
about the floppy disk problem.

It is known that HD (1.4MB) and DD (720kB) is not 
completely downwards compatible on PCs. And as the same
DD disks are being used for the ST, the same problem goes
for that as well.


What are the problems:

1. HD drives use to make thinner tracks than the DD drives.

2. The material structure of the floppies is somewhat
   different. (Note: I'm not an expert in this latter area).


Result:

1. A DD floppy, which is formatted on a DD drive
   will work perfectly.
   However, sometimes problems arises when the data
   written with a HD drive is being read with a 
   DD drive.

2. A DD floppy, which is formatted on a HD drive
   may give problems when used with a DD drive.

3. A HD floppy, formatted on either HD or DD drive
   is a good reason for a lot of problems, when being
   used with a DD drive.


What should you do, to be most-) lucky:

1. Always use a DD floppy disk.

2. Format it with a DD drive.
   (with other words: do not format it as DD with a HD drive)
   So format either on a ST (only when you have TOS 1.4 or a TT),
   or format it on a PC with DD drive.

3. Write the data on the floppy with a DD drive.

This last step is not always necessary, as I found out that when you
did at least step 1 and 2, you have a pretty good chance that the
data written on the DD floppy with a HD drive, can be read in by 
means of a DD drive. However, it may be worthwhile copying the data
to a DD floppy (or Hard disk of course), as you may get problems
in the future.

Hope this helps,

John

--
John Janssen        Check the email address in the header, as this
J.v.Deventerstr.1   may have been filled in wrong by the system.
Venlo Holland
+31 77 513177       Reply to: johnj@idms.prl.philips.nl