Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!ucsd!ucbvax!decwrl!pyramid!prls!philabs!micomvax!ray
From: ray@micomvax.UUCP (Ray Dunn)
Newsgroups: comp.sys.ibm.pc
Subject: Re: 1.2MB drive
Message-ID: <1171@micomvax.UUCP>
Date: 6 Jul 88 21:01:00 GMT
References: <8362@bellcore.bellcore.com>
Reply-To: ray@micomvax.UUCP (Ray Dunn)
Organization: Philips Electronics Ltd. (TDS - Montreal) St. Laurent QC, Canada
Lines: 70

In article <8362@bellcore.bellcore.com> jef@djinn.UUCP (Jonathan E. Flamm) writes:
>I know that there are problems with diskettes written on 1.2MB drives
>when they are read on 360KB drives ( I believe it has to do with only
>1/2 of the track being written due to the narrow track width).  Is there
>software available that will RELIABLY write 360K diskettes on 1.2MB drives
>so they can be reliable read on 360K drives.

There is no *RELIABLE* way of doing this.  The problem is not with software
it is with physics.

There have been several replies saying: "Brand X seems to work fine", "I
have had good luck with...".

Please note that this is *INDEED* a question of luck, and a factor of *both*
the 1.2 Meg drive you are writing on, *and* the 360K drive you are reading
from, *and* the quality of the media you are using.

There is probably a higher correlation between particular *samples* of
drives than between particular manufacturers of drives.

It is indeed true that you increase your chances of success if you format
the disks on a 360K drive.


>I know that there is no problem with the new 3 1/2 1.44MB and 720K formats.

Unfortunately, this is not totally correct, the problems are just a little
more devious!

The early IBM PS/2 machines showed serious interchangeability problems, and
many clone PC's with 3.5 inch drives still do.  Lack of a full specification
standard for 1.4Meg drives is part of the problem, and again, physics comes
into play!

In particular, look for the following problem:

Diskettes formatted on a 720K drive and overwritten on a 1.44 Meg drive (at
720K density) are often then unreadable on a 720K drive.  The severity of
the problem varies very distinctly from drive manufacturer to manufacturer,
and from sample to sample.  It appears to be rare on *current* IBM PS/2
machines.

There are significant interchangeability problems from manufacturer to
manufacturer with 1.4Meg diskettes.  Don't rely on being able to carry a
1.4Meg diskette from your machine to one of a different make!

The fact that early 3.5 inch drives (and some current ones) did not check
the media has caused some grief.  This allows a diskette to be formatted at
the wrong density, i.e. allows a 720K diskette to be formatted as 1.4Meg,
or, just as bad, 1.4Meg as 720K.

Unfortunately, I am not at liberty to identify the worst offenders in the
interchangeability game!!

The above is fact, the following is opinion.

I don't have the info at my fingertips, but I believe some IBM PS/2 machines
may still not lock out illogical format attempts correctly.

As clone manufacturers, we have spent much time and effort identifying and
overcoming these problems.

Disclaimer: The above should be taken as personal opinion of the writer,
            may not reflect that of Philips Electronics Ltd., and is given
            for information purposes only.
-- 
Ray Dunn.                      |   UUCP: ..!{philabs, mnetor}!micomvax!ray
Philips Electronics Ltd.       |   TEL : (514) 744-8200   Ext: 2347
600 Dr Frederik Philips Blvd   |   FAX : (514) 744-6455
St Laurent. Quebec.  H4M 2S9   |   TLX : 05-824090